diff --git a/docs/coding-guidelines/project-guidelines.md b/docs/coding-guidelines/project-guidelines.md
index 457b1da667ff5a..5da61d4ebe2876 100644
--- a/docs/coding-guidelines/project-guidelines.md
+++ b/docs/coding-guidelines/project-guidelines.md
@@ -51,7 +51,7 @@ Non cross-targeting project that targets .NETStandard:
 A cross-targeting project which targets specific platform with `$(NetCoreAppCurrent)` and one .NETFramework tfm:
 ```
 <PropertyGroup>
-  <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetFrameworkMinimum)</TargetFrameworks>
+  <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetFrameworkMinimum)</TargetFrameworks>
 <PropertyGroup>
 ```
 
@@ -103,17 +103,17 @@ Example:
 Example:
 ```
 <PropertyGroup>
-  <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)</TargetFrameworks>
+  <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)</TargetFrameworks>
 </PropertyGroup>
 <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'windows'">...</ItemGroup>
-<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX'">...</ItemGroup>
+<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx'">...</ItemGroup>
 ```
 Important: In contrast to the old `Targets*` checks, `TargetPlatformIdentifier` conditions apply to a single tfm only, inheritance between target frameworks can't be expressed. See the example below for Unix:
 ```
 <PropertyGroup>
-  <TargetFrameworks>$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-windows</TargetFrameworks>
+  <TargetFrameworks>$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-windows</TargetFrameworks>
 </PropertyGroup>
-<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'android'">...</ItemGroup>
+<ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'android'">...</ItemGroup>
 <!-- Negations make such conditions easier to write and read. -->
 <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows'">...</ItemGroup>
 ```
@@ -190,7 +190,7 @@ All test outputs should be under
 In the gen directory any source generator related to the assembly should exist. This does not mean the source generator is only used for that assembly only that it is conceptually apart of that assembly. For example, the assembly may provide attributes or low-level types the source generator uses.
 To consume a source generator, simply add a `<ProjectReference Include="..." ReferenceOutputAssembly="false" OutputItemType="Analyzer" />` item to the project, usually next to the `Reference` and `ProjectReference` items.
 
-A source generator must target `netstandard2.0` as such assemblies are loaded into the compiler's process which might run on either .NET Framework or modern .NET depending on the tooling being used (CLI vs Visual Studio). While that's true, a source project can still multi-target and include `$(NetCoreAppToolCurrent)` (which is the latest non live-built .NETCoreApp tfm that is supported by the SDK) to benefit from the ehancanced nullable reference type warnings emitted by the compiler. For an example see [System.Text.Json's roslyn4.4 source generator](/src/libraries/System.Text.Json/gen/System.Text.Json.SourceGeneration.Roslyn4.4.csproj). While the repository's infrastructure makes sure that only the source generator's `netstandard2.0` build output is included in packages, to consume such a multi-targeting source generator via a `ProjectReference` (as described above), you need to add the `ReferringTargetFramework=netstandard2.0` metadata to the ProjectReference item to guarantee that the netstandard2.0 asset is chosen.
+A source generator must target `netstandard2.0` as such assemblies are loaded into the compiler's process which might run on either .NET Framework or modern .NET depending on the tooling being used (CLI vs Visual Studio). While that's true, a source project can still multi-target and include `$(NetCoreAppToolCurrent)` (which is the latest non live-built .NETCoreApp tfm that is supported by the SDK) to benefit from the ehancanced nullable reference type warnings emitted by the compiler. For an example see [System.Text.Json's roslyn4.4 source generator](/src/libraries/System.Text.Json/gen/System.Text.Json.SourceGeneration.Roslyn4.4.csproj). While the repository's infrastructure makes sure that only the source generator's `netstandard2.0` build output is included in packages, to consume such a multi-targeting source generator via a `ProjectReference` (as described above), you need to add the `SetTargetFramework="TargetFramework=netstandard2.0"` metadata to the ProjectReference item to guarantee that the netstandard2.0 asset is chosen.
 
 ## Facades
 Facade are unique in that they don't have any code and instead are generated by finding a contract reference assembly with the matching identity and generating type forwards for all the types to where they live in the implementation assemblies (aka facade seeds). There are also partial facades which contain some type forwards as well as some code definitions. All the various build configurations should be contained in the one csproj file per library.
diff --git a/eng/Version.Details.xml b/eng/Version.Details.xml
index 6e81ec5bc802a2..a6e1acd921eb04 100644
--- a/eng/Version.Details.xml
+++ b/eng/Version.Details.xml
@@ -142,7 +142,7 @@
       <Uri>https://github.com/dotnet/arcade</Uri>
       <Sha>3003926e4126f827bca50d5b3ee179afc86d8a7b</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.Build.Tasks.TargetFramework" Version="8.0.0-beta.22621.1">
+    <Dependency Name="Microsoft.DotNet.Build.Tasks.TargetFramework" Version="8.0.0-beta.22630.1">
       <Uri>https://github.com/dotnet/arcade</Uri>
       <Sha>3003926e4126f827bca50d5b3ee179afc86d8a7b</Sha>
     </Dependency>
diff --git a/eng/Versions.props b/eng/Versions.props
index 2f8499768cca61..85063175435288 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -90,7 +90,7 @@
     <MicrosoftDotNetBuildTasksArchivesVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksArchivesVersion>
     <MicrosoftDotNetBuildTasksInstallersVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksInstallersVersion>
     <MicrosoftDotNetBuildTasksPackagingVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksPackagingVersion>
-    <MicrosoftDotNetBuildTasksTargetFrameworkVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksTargetFrameworkVersion>
+    <MicrosoftDotNetBuildTasksTargetFrameworkVersion>8.0.0-beta.23052.2</MicrosoftDotNetBuildTasksTargetFrameworkVersion>
     <MicrosoftDotNetBuildTasksTemplatingVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksTemplatingVersion>
     <MicrosoftDotNetBuildTasksWorkloadsPackageVersion>8.0.0-beta.22621.1</MicrosoftDotNetBuildTasksWorkloadsPackageVersion>
     <MicrosoftDotNetRemoteExecutorVersion>8.0.0-beta.22621.1</MicrosoftDotNetRemoteExecutorVersion>
diff --git a/eng/illink.targets b/eng/illink.targets
index e574f066166bf5..0f300e1a02d3ab 100644
--- a/eng/illink.targets
+++ b/eng/illink.targets
@@ -60,18 +60,18 @@
        Must be enabled by setting BinPlaceILLinkTrimAssembly=true
   -->
   <ItemGroup Condition="'$(BinPlaceILLinkTrimAssembly)' == 'true'">
-    <BinPlaceTargetFramework Include="$(NetCoreAppCurrentBuildSettings)">
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrentBuildSettings)">
       <RuntimePath>$(ILLinkTrimAssemblyArtifactsRootDir)trimmed</RuntimePath>
       <ItemName>TrimmedItem</ItemName>
-    </BinPlaceTargetFramework>
-    <BinPlaceTargetFramework Include="$(NetCoreAppCurrentBuildSettings)">
+    </BinPlaceTargetFrameworks>
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrentBuildSettings)">
       <RuntimePath>$(ILLinkTrimAssemblyArtifactsRootDir)reports</RuntimePath>
       <ItemName>TrimmingReport</ItemName>
-    </BinPlaceTargetFramework>
-    <BinPlaceTargetFramework Include="$(NetCoreAppCurrentBuildSettings)">
+    </BinPlaceTargetFrameworks>
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrentBuildSettings)">
       <RuntimePath>$(ILLinkTrimAssemblyArtifactsRootDir)pretrimmed</RuntimePath>
       <ItemName>PreTrimmedItem</ItemName>
-    </BinPlaceTargetFramework>
+    </BinPlaceTargetFrameworks>
   </ItemGroup>
 
   <ItemGroup>
@@ -89,7 +89,7 @@
       <RuntimePath>$(ILLinkTrimAssemblySuppressionsXmlsDir)</RuntimePath>
       <ItemName>ILLinkSuppressionsXmls</ItemName>
     </BinPlaceTargetFrameworks>
-    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS)">
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())">
       <RuntimePath>$(ILLinkTrimAssemblySuppressionsXmlsDir)</RuntimePath>
       <ItemName>ILLinkSuppressionsXmls</ItemName>
     </BinPlaceTargetFrameworks>
diff --git a/eng/packaging.targets b/eng/packaging.targets
index 210a4264604eb8..e5cfa659cfaf97 100644
--- a/eng/packaging.targets
+++ b/eng/packaging.targets
@@ -12,8 +12,8 @@
     <BeforePack>$(BeforePack);IncludeAnalyzersInPackage;AddNETStandardCompatErrorFileForPackaging</BeforePack>
     <TargetsForTfmSpecificContentInPackage>$(TargetsForTfmSpecificContentInPackage);AddRuntimeSpecificFilesToPackage;IncludeProjectReferencesWithPackAttributeInPackage</TargetsForTfmSpecificContentInPackage>
     <!-- Don't include target platform specific dependencies, since we use the target platform to represent RIDs instead -->
-    <IncludeBuildOutput Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetFrameworkIdentifier)' == '.NETCoreApp'">false</IncludeBuildOutput>
-    <SuppressDependenciesWhenPacking Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetFrameworkIdentifier)' == '.NETCoreApp'">true</SuppressDependenciesWhenPacking>
+    <IncludeBuildOutput Condition="'$(PackageUsePlatformTargeting)' != 'true' and '$(TargetPlatformIdentifier)' != '' and '$(TargetFrameworkIdentifier)' == '.NETCoreApp'">false</IncludeBuildOutput>
+    <SuppressDependenciesWhenPacking Condition="'$(PackageUsePlatformTargeting)' != 'true' and '$(TargetPlatformIdentifier)' != '' and '$(TargetFrameworkIdentifier)' == '.NETCoreApp'">true</SuppressDependenciesWhenPacking>
     <PackageDesignerMarkerFile>$(MSBuildThisFileDirectory)useSharedDesignerContext.txt</PackageDesignerMarkerFile>
     <PackageReadmeFile Condition="'$(PackageReadmeFile)' == '' and Exists('PACKAGE.md')">PACKAGE.md</PackageReadmeFile>
     <!-- Generate packages for rid specific projects or for allconfigurations during build. -->
@@ -31,6 +31,8 @@
     <!-- Search for the documentation file in the intellisense package and otherwise pick up the generated one. -->
     <LibIntellisenseDocumentationFilePath>$(XmlDocFileRoot)1033\$(AssemblyName).xml</LibIntellisenseDocumentationFilePath>
     <UseIntellisenseDocumentationFile Condition="'$(UseIntellisenseDocumentationFile)' == '' and Exists('$(LibIntellisenseDocumentationFilePath)')">true</UseIntellisenseDocumentationFile>
+    <!-- During NoBuild pack invocations, skip project reference build. Necessary for the IncludeProjectReferencesWithPackAttributeInPackage target. -->
+    <BuildProjectReferences Condition="'$(NoBuild)' == 'true'">false</BuildProjectReferences>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(PreReleaseVersionLabel)' == 'servicing' and
@@ -122,7 +124,8 @@
                             DocumentationProjectOutputGroup;
                             SatelliteDllsProjectOutputGroup;
                             $(TargetsForTfmSpecificBuildOutput)"
-          Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp' and
+          Condition="'$(PackageUsePlatformTargeting)' != 'true' and
+                     '$(TargetFrameworkIdentifier)' == '.NETCoreApp' and
                      '$(TargetPlatformIdentifier)' != ''">
     <PropertyGroup>
       <RuntimeSymbolPath>$(TargetDir)$(TargetName).pdb</RuntimeSymbolPath>
@@ -244,14 +247,19 @@
   <Target Name="IncludeProjectReferencesWithPackAttributeInPackage"
           Condition="'@(ProjectReference)' != '' and @(ProjectReference->AnyHaveMetadataValue('Pack', 'true'))"
           DependsOnTargets="BuildOnlySettings;ResolveReferences">
+    <PropertyGroup>
+      <_referringTargetFramework>$(TargetFramework)</_referringTargetFramework>
+      <_referringTargetFramework Condition="'$(PackageUsePlatformTargeting)' != 'true' and $(TargetFramework.Contains('-'))">$(TargetFramework.SubString(0, $(TargetFramework.IndexOf('-'))))</_referringTargetFramework>
+    </PropertyGroup>
+
     <ItemGroup>
       <!-- Add ReferenceCopyLocalPaths for ProjectReferences which are flagged as Pack="true" into the package. -->
       <_projectReferenceCopyLocalPaths Include="@(ReferenceCopyLocalPaths->WithMetadataValue('ReferenceSourceTarget', 'ProjectReference')->WithMetadataValue('Pack', 'true'))" />
       <TfmSpecificPackageFile Include="@(_projectReferenceCopyLocalPaths)"
-                              PackagePath="$([MSBuild]::ValueOrDefault('%(ReferenceCopyLocalPaths.PackagePath)', '$(BuildOutputTargetFolder)\$(TargetFramework)\'))" />
+                              PackagePath="$([MSBuild]::ValueOrDefault('%(ReferenceCopyLocalPaths.PackagePath)', '$(BuildOutputTargetFolder)\$(_referringTargetFramework)\'))" />
       <TfmSpecificDebugSymbolsFile Include="@(TfmSpecificPackageFile->WithMetadataValue('Extension', '.pdb'))"
                                    TargetPath="/%(TfmSpecificPackageFile.PackagePath)/%(Filename)%(Extension)"
-                                   TargetFramework="$(TargetFramework)"
+                                   TargetFramework="$(_referringTargetFramework)"
                                    Condition="'$(IncludeSymbols)' == 'true'" />
       <!-- Remove symbol from the non symbol package. -->
       <TfmSpecificPackageFile Remove="@(TfmSpecificPackageFile->WithMetadataValue('Extension', '.pdb'))" />
@@ -264,7 +272,7 @@
       <_referenceAssemblyPaths Include="@(_projectReferenceCopyLocalPaths->WithMetadataValue('Extension', '.dll')->WithMetadataValue('IncludeReferenceAssemblyInPackage', 'true')->Metadata('ReferenceAssembly'))" />
       <_referenceAssemblyPaths Include="@(_projectReferenceCopyLocalPaths->WithMetadataValue('Extension', '.xml')->WithMetadataValue('IncludeReferenceAssemblyInPackage', 'true'))" />
       <TfmSpecificPackageFile Include="@(_referenceAssemblyPaths)"
-                              PackagePath="ref\$(TargetFramework)\" />
+                              PackagePath="ref\$(_referringTargetFramework)\" />
     </ItemGroup>
   </Target>
 
diff --git a/eng/resolveContract.targets b/eng/resolveContract.targets
index e7d894b5d1dc90..441286ab84bfe6 100644
--- a/eng/resolveContract.targets
+++ b/eng/resolveContract.targets
@@ -23,10 +23,18 @@
 
   <ItemGroup Condition="'$(HasMatchingContract)' == 'true' and '$(ContractProject)' != ''">
     <ProjectReference Include="$(ContractProject)" ReferenceOutputAssembly="false" OutputItemType="ResolvedMatchingContract" />
-    <!-- We aren't referencing the contract, but make sure it's considered as an input to Compile so that if it changes we rebuild and rerun API compat -->
-    <ProjectReference Include="$(ContractProject)" ReferenceOutputAssembly="false" OutputItemType="CustomAdditionalCompileInputs" />
   </ItemGroup>
 
+  <!-- We aren't referencing the contract, but make sure it's considered as an input to Compile so that if it changes we rebuild and rerun API compat -->
+  <Target Name="AddResolvedMatchingContractToCompileInput"
+          BeforeTargets="CoreCompile"
+          AfterTargets="ResolveProjectReferences"
+          Condition="'@(ResolvedMatchingContract)' != ''">
+    <ItemGroup>
+      <CustomAdditionalCompileInputs Include="@(ResolvedMatchingContract)" />
+    </ItemGroup>
+  </Target>
+
   <!-- Allow P2Ps that target a source project to build against the corresponding ref project. -->
   <Target Name="AnnotateTargetPathWithTargetPlatformMonikerWithReferenceAssembly"
           Condition="'$(AnnotateTargetPathWithContract)' == 'true'"
diff --git a/eng/versioning.targets b/eng/versioning.targets
index d5191990135999..1e251f645b3272 100644
--- a/eng/versioning.targets
+++ b/eng/versioning.targets
@@ -62,7 +62,7 @@
     </ItemGroup>
   </Target>
 
-  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == '' and !$(TargetFrameworks.Contains('$(TargetFramework)-Browser'))">
+  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == '' and !$(TargetFrameworks.Contains('$(TargetFramework)-browser'))">
     <CrossPlatformAndHasNoBrowserTarget>true</CrossPlatformAndHasNoBrowserTarget>
   </PropertyGroup>
 
@@ -75,17 +75,17 @@
   </ItemGroup>
 
   <!-- Enables browser warnings for cross platform or Browser targeted builds -->
-  <ItemGroup Condition="('$(TargetPlatformIdentifier)' == 'Browser' or '$(CrossPlatformAndHasNoBrowserTarget)' == 'true') and '$(IsTestProject)' != 'true'">
+  <ItemGroup Condition="('$(TargetPlatformIdentifier)' == 'browser' or '$(CrossPlatformAndHasNoBrowserTarget)' == 'true') and '$(IsTestProject)' != 'true'">
     <SupportedPlatform Include="browser"/>
   </ItemGroup>
 
   <!-- Add target platforms into MSBuild SupportedPlatform list -->
   <ItemGroup Condition="'$(IsTestProject)' != 'true'">
     <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' == 'illumos'" Include="illumos" />
-    <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' == 'Solaris'" Include="Solaris" />
-    <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' == 'tvOS'" Include="tvOS" />
+    <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' == 'solaris'" Include="Solaris" />
+    <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' == 'tvos'" Include="tvOS" />
     <SupportedPlatform Condition="'$(TargetPlatformIdentifier)' != '' and
-                                  '$(TargetPlatformIdentifier)' != 'Browser' and
+                                  '$(TargetPlatformIdentifier)' != 'browser' and
                                   '$(TargetPlatformIdentifier)' != 'wasi' and
                                   '$(TargetPlatformIdentifier)' != 'windows'" Include="Unix" />
   </ItemGroup>
diff --git a/src/libraries/Common/tests/Common.Tests.csproj b/src/libraries/Common/tests/Common.Tests.csproj
index 72de3a2ba178b0..709b8cc72a2264 100644
--- a/src/libraries/Common/tests/Common.Tests.csproj
+++ b/src/libraries/Common/tests/Common.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <ItemGroup>
@@ -139,12 +139,12 @@
              Link="System\PasteArguments.Unix.cs" />
   </ItemGroup>
   <!-- Linux specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs"
              Link="Common\Interop\Linux\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- OSX specific files -->
-  <ItemGroup Condition=" '$(TargetPlatformIdentifier)' == 'OSX' ">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
              Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/Directory.Build.props b/src/libraries/Directory.Build.props
index 55dbcfd2cb1094..d17a577688e153 100644
--- a/src/libraries/Directory.Build.props
+++ b/src/libraries/Directory.Build.props
@@ -8,7 +8,6 @@
 
   <PropertyGroup>
     <BeforeTargetFrameworkInferenceTargets>$(RepositoryEngineeringDir)BeforeTargetFrameworkInference.targets</BeforeTargetFrameworkInferenceTargets>
-    <RuntimeGraph>$(LibrariesProjectRoot)OSGroups.json</RuntimeGraph>
     <ShouldUnsetParentConfigurationAndPlatform>false</ShouldUnsetParentConfigurationAndPlatform>
     <GeneratePlatformNotSupportedAssemblyHeaderFile>$(RepositoryEngineeringDir)LicenseHeader.txt</GeneratePlatformNotSupportedAssemblyHeaderFile>
   </PropertyGroup>
diff --git a/src/libraries/Directory.Build.targets b/src/libraries/Directory.Build.targets
index c7decd2eade995..d35efae24385b7 100644
--- a/src/libraries/Directory.Build.targets
+++ b/src/libraries/Directory.Build.targets
@@ -88,9 +88,9 @@
     </ItemGroup>
   </Target>
 
-  <ItemGroup Condition="'@(BinPlaceTargetFrameworks)' == ''">
+  <ItemGroup>
     <!-- Used by the runtime tests to prepare the CORE_ROOT layout. Don't use in libraries. -->
-    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS)"
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())"
                               Condition="'$(BinPlaceForTargetVertical)' == 'true'">
       <NativePath>$(LibrariesAllBinArtifactsPath)</NativePath>
       <RefPath>$(LibrariesAllRefArtifactsPath)</RefPath>
@@ -103,19 +103,17 @@
                             '$(TargetFramework)' == 'netstandard2.0'" />
 
     <!-- Setup the shared framework directory for testing -->
-    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS)">
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())">
       <NativePath>$(NetCoreAppCurrentTestHostSharedFrameworkPath)</NativePath>
       <RuntimePath Condition="'$(IsNETCoreAppSrc)' == 'true'">$(NetCoreAppCurrentTestHostSharedFrameworkPath)</RuntimePath>
     </BinPlaceTargetFrameworks>
 
     <!-- Microsoft.NetCore.App.Ref and Microsoft.NetCore.App.Runtime targeting packs -->
-    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS)">
+    <BinPlaceTargetFrameworks Include="$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())">
       <NativePath>$(MicrosoftNetCoreAppRuntimePackNativeDir)</NativePath>
       <RefPath Condition="'$(IsNETCoreAppRef)' == 'true'">$(MicrosoftNetCoreAppRefPackRefDir)</RefPath>
       <RuntimePath Condition="'$(IsNETCoreAppSrc)' == 'true'">$(MicrosoftNetCoreAppRuntimePackRidLibTfmDir)</RuntimePath>
     </BinPlaceTargetFrameworks>
-
-    <BinPlaceTargetFrameworks Include="@(AdditionalBinPlaceTargetFrameworks)" />
   </ItemGroup>
 
   <Import Project="$(RepositoryEngineeringDir)targetingpacks.targets" />
diff --git a/src/libraries/Microsoft.Internal.Runtime.WindowsDesktop.Transport/src/Microsoft.Internal.Runtime.WindowsDesktop.Transport.proj b/src/libraries/Microsoft.Internal.Runtime.WindowsDesktop.Transport/src/Microsoft.Internal.Runtime.WindowsDesktop.Transport.proj
index 9f1d2aca1b91f0..1be506a457ae6c 100644
--- a/src/libraries/Microsoft.Internal.Runtime.WindowsDesktop.Transport/src/Microsoft.Internal.Runtime.WindowsDesktop.Transport.proj
+++ b/src/libraries/Microsoft.Internal.Runtime.WindowsDesktop.Transport/src/Microsoft.Internal.Runtime.WindowsDesktop.Transport.proj
@@ -1,16 +1,15 @@
 <Project Sdk="Microsoft.Build.NoTargets">
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-windows</TargetFramework>
     <IsShipping>false</IsShipping>
     <!-- Reference the outputs to have them available as build outputs. -->
     <NoTargetsDoNotReferenceOutputAssemblies>false</NoTargetsDoNotReferenceOutputAssemblies>
     <IsPackable>true</IsPackable>
-    <IncludeBuildOutput>true</IncludeBuildOutput>
     <!-- TODO: Enable APICompat: https://github.com/dotnet/runtime/issues/52562. -->
     <EnablePackageValidation>false</EnablePackageValidation>
     <PackageDescription>Internal transport package to provide windowsdesktop with the assemblies from dotnet/runtime that make up the Microsoft.WindowsDesktop.App shared framework.</PackageDescription>
     <!-- Reference elements are missing from the nuspec: https://github.com/NuGet/Home/issues/8684. -->
-    <NoWarn>$(NoWarn);NU5131</NoWarn>
+    <NoWarn>$(NoWarn);NU5131;NU5128</NoWarn>
   </PropertyGroup>
 
   <!-- Always generate this package during servicing to flow the dependency to WindowsDesktop. -->
@@ -24,7 +23,6 @@
          ReferringTargetFramework is set to $(NetCoreAppCurrent)-windows so that we pack the Windows specific implementation assemblies -->
     <ProjectReference Include="@(WindowsDesktopCoreAppLibrary->'$(LibrariesProjectRoot)%(Identity)\src\%(Identity).csproj');
                                $(LibrariesProjectRoot)System.Diagnostics.EventLog\src\Messages\System.Diagnostics.EventLog.Messages.csproj"
-                      ReferringTargetFramework="$(NetCoreAppCurrent)-windows"
                       PrivateAssets="all"
                       Pack="true"
                       Private="true"
diff --git a/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj b/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj
index aa61641a9fa94a..c058f772a8cf6c 100644
--- a/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj
+++ b/src/libraries/Microsoft.Win32.Primitives/tests/Microsoft.Win32.Primitives.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Win32ExceptionTests.cs" />
diff --git a/src/libraries/OSGroups.json b/src/libraries/OSGroups.json
deleted file mode 100644
index 2c6aa55fb00e7f..00000000000000
--- a/src/libraries/OSGroups.json
+++ /dev/null
@@ -1,70 +0,0 @@
-{
-  "runtimes": {
-    "Unix" : {
-    },
-    "Browser" : {
-    },
-    "wasi" : {
-    },
-    "Linux": {
-      "#import": [
-          "Unix"
-        ]
-      },
-    "OSX": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "MacCatalyst": {
-      "#import": [
-        "iOS"
-        ]
-      },
-    "iOS": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "iOSSimulator": {
-      "#import": [
-        "iOS"
-        ]
-      },
-    "tvOS": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "tvOSSimulator": {
-      "#import": [
-        "tvOS"
-        ]
-      },
-    "Android": {
-      "#import": [
-        "Linux"
-        ]
-      },
-    "FreeBSD": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "NetBSD": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "illumos": {
-      "#import": [
-        "Unix"
-        ]
-      },
-    "Solaris": {
-      "#import": [
-        "Unix"
-        ]
-      }
-    }
-}
diff --git a/src/libraries/System.Console/src/System.Console.csproj b/src/libraries/System.Console/src/System.Console.csproj
index 2097f08efe7162..7892e19b467295 100644
--- a/src/libraries/System.Console/src/System.Console.csproj
+++ b/src/libraries/System.Console/src/System.Console.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -30,7 +30,7 @@
              Link="Common\System\Text\ValueStringBuilder.AppendSpanFormattable.cs" />
   </ItemGroup>
   <!-- iOS/tvOS -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="System\ConsolePal.iOS.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Log.cs"
              Link="Common\Interop\Unix\Interop.Log.cs" />
@@ -38,7 +38,7 @@
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- Android -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Android'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'android'">
     <Compile Include="System\ConsolePal.Android.cs" />
     <Compile Include="$(CommonPath)Interop\Android\Interop.Logcat.cs">
       <Link>Common\Interop\Android\Interop.Logcat.cs</Link>
@@ -48,7 +48,7 @@
     </Compile>
   </ItemGroup>
   <!-- WebAssembly -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\ConsolePal.WebAssembly.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Dup.cs"
              Link="Common\Interop\Unix\Interop.Dup.cs" />
@@ -156,7 +156,7 @@
              Link="Common\System\IO\Win32Marshal.cs" />
   </ItemGroup>
   <!-- Unix -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\ConsolePal.Unix.cs" />
     <Compile Include="System\TerminalFormatStrings.cs" />
     <Compile Include="$(CommonPath)System\Console\ConsoleUtils.cs"
@@ -235,7 +235,7 @@
     <Reference Include="System.Threading" />
     <Reference Include="Microsoft.Win32.Primitives" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\gen\JSImportGenerator\JSImportGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     <Reference Include="System.Runtime.InteropServices.JavaScript" />
   </ItemGroup>
diff --git a/src/libraries/System.Data.Odbc/src/System.Data.Odbc.csproj b/src/libraries/System.Data.Odbc/src/System.Data.Odbc.csproj
index a6fae5dcd35e18..7c1e49348ad9a7 100644
--- a/src/libraries/System.Data.Odbc/src/System.Data.Odbc.csproj
+++ b/src/libraries/System.Data.Odbc/src/System.Data.Odbc.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-FreeBSD;$(NetCoreAppPrevious)-illumos;$(NetCoreAppPrevious)-Solaris;$(NetCoreAppPrevious)-Linux;$(NetCoreAppPrevious)-OSX;$(NetCoreAppPrevious)-iOS;$(NetCoreAppPrevious)-tvOS;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-FreeBSD;$(NetCoreAppMinimum)-Linux;$(NetCoreAppMinimum)-OSX;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-freebsd;$(NetCoreAppPrevious)-illumos;$(NetCoreAppPrevious)-solaris;$(NetCoreAppPrevious)-linux;$(NetCoreAppPrevious)-osx;$(NetCoreAppPrevious)-ios;$(NetCoreAppPrevious)-tvos;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-freebsd;$(NetCoreAppMinimum)-linux;$(NetCoreAppMinimum)-osx;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <NoWarn>$(NoWarn);CA2249;CA1838;CA1846</NoWarn>
     <!-- Suppress CA1845: Use span-based 'string.Concat' and 'AsSpan' instead of 'Substring' to avoid ifdefs. -->
@@ -137,12 +137,12 @@ System.Data.Odbc.OdbcTransaction</PackageDescription>
              Link="Common\System\Runtime\InteropServices\HandleRefMarshaller.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'FreeBSD' or '$(TargetPlatformIdentifier)' == 'illumos' or '$(TargetPlatformIdentifier)' == 'Solaris'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'freebsd' or '$(TargetPlatformIdentifier)' == 'illumos' or '$(TargetPlatformIdentifier)' == 'solaris'">
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs"
              Link="Common\Interop\Linux\Interop.Libraries.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
              Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Data.Odbc/tests/System.Data.Odbc.Tests.csproj b/src/libraries/System.Data.Odbc/tests/System.Data.Odbc.Tests.csproj
index 85a15ebe3d2415..c208fe67433a9d 100644
--- a/src/libraries/System.Data.Odbc/tests/System.Data.Odbc.Tests.csproj
+++ b/src/libraries/System.Data.Odbc/tests/System.Data.Odbc.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetFrameworkMinimum)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -23,15 +23,15 @@
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux'">
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs"
              Link="Common\Interop\Linux\Interop.Libraries.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
              Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="$(CommonPath)Interop\FreeBSD\Interop.Libraries.cs"
              Link="Common\Interop\FreeBSD\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj b/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj
index 601c003fc30266..501daeabf92027 100644
--- a/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj
+++ b/src/libraries/System.Diagnostics.Debug/tests/System.Diagnostics.Debug.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <RootNamespace>System.Diagnostics.Tests</RootNamespace>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix</TargetFrameworks>
     <TestRuntime>true</TestRuntime>
     <!-- Some tests need types like System.Diagnostics.DebugProvider which are only exposed from System.Private.CoreLib -->
     <CompileUsingReferenceAssemblies>false</CompileUsingReferenceAssemblies>
diff --git a/src/libraries/System.Diagnostics.FileVersionInfo/src/System.Diagnostics.FileVersionInfo.csproj b/src/libraries/System.Diagnostics.FileVersionInfo/src/System.Diagnostics.FileVersionInfo.csproj
index 183b62c5283202..5c8eaffab0a6d7 100644
--- a/src/libraries/System.Diagnostics.FileVersionInfo/src/System.Diagnostics.FileVersionInfo.csproj
+++ b/src/libraries/System.Diagnostics.FileVersionInfo/src/System.Diagnostics.FileVersionInfo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -32,7 +32,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\Version\Interop.VSFixedFileInfo.cs"
              Link="Common\Interop\Windows\Interop.VSFixedFileInfo.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\Diagnostics\FileVersionInfo.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
@@ -46,7 +46,7 @@
     <Reference Include="System.Runtime" />
     <Reference Include="System.Runtime.InteropServices" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Reference Include="System.Collections.Immutable" />
     <Reference Include="System.Reflection.Metadata" />
   </ItemGroup>
diff --git a/src/libraries/System.Diagnostics.FileVersionInfo/tests/System.Diagnostics.FileVersionInfo.Tests/System.Diagnostics.FileVersionInfo.Tests.csproj b/src/libraries/System.Diagnostics.FileVersionInfo/tests/System.Diagnostics.FileVersionInfo.Tests/System.Diagnostics.FileVersionInfo.Tests.csproj
index ba53223e2e8cba..08047ad205e850 100644
--- a/src/libraries/System.Diagnostics.FileVersionInfo/tests/System.Diagnostics.FileVersionInfo.Tests/System.Diagnostics.FileVersionInfo.Tests.csproj
+++ b/src/libraries/System.Diagnostics.FileVersionInfo/tests/System.Diagnostics.FileVersionInfo.Tests/System.Diagnostics.FileVersionInfo.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
@@ -38,7 +38,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\Kernel32\Interop.VerLanguageName.cs"
              Link="ProductionCode\Common\Interop\Windows\Kernel32\Interop.VerLanguageName.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="FileVersionInfoTest.Unix.cs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj b/src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj
index 6f729f78ed0a48..e82e069ffd3ed5 100644
--- a/src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj
+++ b/src/libraries/System.Diagnostics.Process/src/System.Diagnostics.Process.csproj
@@ -2,13 +2,13 @@
   <PropertyGroup>
     <DefineConstants>$(DefineConstants);FEATURE_REGISTRY</DefineConstants>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.Process_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
-    <IsiOSLike Condition="'$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</IsiOSLike>
+    <IsiOSLike Condition="'$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</IsiOSLike>
   </PropertyGroup>
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != ''">
     <Compile Include="Microsoft\Win32\SafeHandles\SafeProcessHandle.cs" />
@@ -290,7 +290,7 @@
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(IsiOSLike)' == 'true'">
     <Compile Include="System\Diagnostics\Process.ConfigureTerminalForChildProcesses.iOS.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux'">
     <Compile Include="System\Diagnostics\Process.Linux.cs" />
     <Compile Include="System\Diagnostics\ProcessManager.Linux.cs" />
     <Compile Include="System\Diagnostics\ProcessThread.Linux.cs" />
@@ -307,7 +307,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.SchedGetSetAffinity.cs"
              Link="Common\Interop\Linux\Interop.SchedGetSetAffinity.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'MacCatalyst'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'maccatalyst'">
     <Compile Include="System\Diagnostics\Process.BSD.cs" />
     <Compile Include="System\Diagnostics\Process.OSX.cs" />
     <Compile Include="System\Diagnostics\ProcessManager.BSD.cs" />
@@ -327,10 +327,10 @@
     <Compile Include="System\Diagnostics\ProcessManager.Win32.cs" />
     <Compile Include="System\Diagnostics\ProcessStartInfo.Win32.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'tvos'">
     <Compile Include="System\Diagnostics\Process.NonUap.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="System\Diagnostics\Process.BSD.cs" />
     <Compile Include="System\Diagnostics\Process.FreeBSD.cs" />
     <Compile Include="System\Diagnostics\ProcessManager.BSD.cs" />
@@ -343,7 +343,7 @@
     <Compile Include="$(CommonPath)Interop\FreeBSD\Interop.Process.GetProcInfo.cs"
              Link="Common\Interop\FreeBSD\Interop.Process.GetProcInfo.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="System\Diagnostics\Process.iOS.cs" />
     <Compile Include="System\Diagnostics\ProcessManager.iOS.cs" />
     <Compile Include="System\Diagnostics\ProcessThread.iOS.cs" />
diff --git a/src/libraries/System.Diagnostics.Process/tests/System.Diagnostics.Process.Tests.csproj b/src/libraries/System.Diagnostics.Process/tests/System.Diagnostics.Process.Tests.csproj
index 78a4b99602aa80..83b1df051ccdc5 100644
--- a/src/libraries/System.Diagnostics.Process/tests/System.Diagnostics.Process.Tests.csproj
+++ b/src/libraries/System.Diagnostics.Process/tests/System.Diagnostics.Process.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
@@ -57,7 +57,7 @@
     <!-- Helpers -->
     <Compile Include="$(CommonTestPath)TestUtilities\System\WindowsTestFileShare.cs" Link="Common\TestUtilities\System\WindowsTestFileShare.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="Interop.Unix.cs" />
     <Compile Include="ProcessTests.Unix.cs" />
     <Compile Include="ProcessThreadTests.Unix.cs" />
diff --git a/src/libraries/System.DirectoryServices.Protocols/src/System.DirectoryServices.Protocols.csproj b/src/libraries/System.DirectoryServices.Protocols/src/System.DirectoryServices.Protocols.csproj
index 8df69203635b5e..1d3aa9095e9b1f 100644
--- a/src/libraries/System.DirectoryServices.Protocols/src/System.DirectoryServices.Protocols.csproj
+++ b/src/libraries/System.DirectoryServices.Protocols/src/System.DirectoryServices.Protocols.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-OSX;$(NetCoreAppPrevious)-Linux;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-OSX;$(NetCoreAppMinimum)-Linux;$(NetCoreAppMinimum);netstandard2.0</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-osx;$(NetCoreAppPrevious)-linux;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-osx;$(NetCoreAppMinimum)-linux;$(NetCoreAppMinimum);netstandard2.0</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeDllSafeSearchPathAttribute>true</IncludeDllSafeSearchPathAttribute>
     <IsPackable>true</IsPackable>
@@ -77,7 +77,7 @@
     </Compile>
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="System\DirectoryServices\Protocols\common\BerConverter.Linux.cs" />
     <Compile Include="System\DirectoryServices\Protocols\common\QuotaControl.Linux.cs" />
     <Compile Include="System\DirectoryServices\Protocols\Interop\LdapPal.Linux.cs" />
@@ -98,13 +98,13 @@
     </Compile>
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux'">
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs">
       <Link>Common\Interop\Linux\Interop.Libraries.cs</Link>
     </Compile>
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs">
       <Link>Common\Interop\OSX\Interop.Libraries.cs</Link>
     </Compile>
diff --git a/src/libraries/System.DirectoryServices.Protocols/tests/System.DirectoryServices.Protocols.Tests.csproj b/src/libraries/System.DirectoryServices.Protocols/tests/System.DirectoryServices.Protocols.Tests.csproj
index 9a78a3acd54387..08a5d52cadcf8b 100644
--- a/src/libraries/System.DirectoryServices.Protocols/tests/System.DirectoryServices.Protocols.Tests.csproj
+++ b/src/libraries/System.DirectoryServices.Protocols/tests/System.DirectoryServices.Protocols.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;net48</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;net48</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="BerConverterTests.cs" />
diff --git a/src/libraries/System.Dynamic.Runtime/tests/System.Dynamic.Runtime.Tests.csproj b/src/libraries/System.Dynamic.Runtime/tests/System.Dynamic.Runtime.Tests.csproj
index 57195bfe5aad1c..38bc2f67d0b3d8 100644
--- a/src/libraries/System.Dynamic.Runtime/tests/System.Dynamic.Runtime.Tests.csproj
+++ b/src/libraries/System.Dynamic.Runtime/tests/System.Dynamic.Runtime.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <NoWarn>67,168,219,414,162,184,458,464,78,169,114,693,108,1981,649,109,1066,3021,3026,3002,3014,3022,660,661,429;xUnit1013</NoWarn>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-MacCatalyst</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-maccatalyst</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <AssembliesBeingTested Include="Microsoft.CSharp" />
diff --git a/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj b/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
index 33a9aa8c1dc0cb..956b62072670d9 100644
--- a/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
+++ b/src/libraries/System.Formats.Tar/src/System.Formats.Tar.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
@@ -50,7 +50,7 @@
     <Compile Include="$(CommonPath)System\Text\ValueStringBuilder.cs" Link="Common\System\Text\ValueStringBuilder.cs" />
   </ItemGroup>
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\Formats\Tar\TarEntry.Unix.cs" />
     <Compile Include="System\Formats\Tar\TarHelpers.Unix.cs" />
     <Compile Include="System\Formats\Tar\TarWriter.Unix.cs" />
diff --git a/src/libraries/System.Formats.Tar/tests/System.Formats.Tar.Tests.csproj b/src/libraries/System.Formats.Tar/tests/System.Formats.Tar.Tests.csproj
index 7ec67c69fc964b..cf0cf80d2f5900 100644
--- a/src/libraries/System.Formats.Tar/tests/System.Formats.Tar.Tests.csproj
+++ b/src/libraries/System.Formats.Tar/tests/System.Formats.Tar.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>$(MSBuildProjectDirectory)\..\src\Resources\Strings.resx</StringResourcesPath>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
diff --git a/src/libraries/System.IO.Compression.Brotli/src/System.IO.Compression.Brotli.csproj b/src/libraries/System.IO.Compression.Brotli/src/System.IO.Compression.Brotli.csproj
index ced12496d65b87..6c884b2ee6d96d 100644
--- a/src/libraries/System.IO.Compression.Brotli/src/System.IO.Compression.Brotli.csproj
+++ b/src/libraries/System.IO.Compression.Brotli/src/System.IO.Compression.Brotli.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -31,7 +31,7 @@
              Link="Common\Interop\Windows\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' ">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' ">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.IO.Compression.Brotli/tests/System.IO.Compression.Brotli.Tests.csproj b/src/libraries/System.IO.Compression.Brotli/tests/System.IO.Compression.Brotli.Tests.csproj
index 709f655902dab3..afb5a269db9117 100644
--- a/src/libraries/System.IO.Compression.Brotli/tests/System.IO.Compression.Brotli.Tests.csproj
+++ b/src/libraries/System.IO.Compression.Brotli/tests/System.IO.Compression.Brotli.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
   </PropertyGroup>
diff --git a/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj b/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
index 29c88cb2f9ce2e..2b314ba27a2c38 100644
--- a/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
+++ b/src/libraries/System.IO.Compression.ZipFile/tests/System.IO.Compression.ZipFile.Tests.csproj
@@ -3,7 +3,7 @@
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetOS)' == 'Browser'">
@@ -37,7 +37,7 @@
     <Compile Include="$(CommonTestPath)System\IO\Compression\ZipTestHelper.cs"
              Link="Common\System\IO\Compression\ZipTestHelper.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="ZipFile.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs" Link="Interop\Unix\System.Native\Interop.Stat.cs" />
diff --git a/src/libraries/System.IO.Compression/src/System.IO.Compression.csproj b/src/libraries/System.IO.Compression/src/System.IO.Compression.csproj
index 150b3efdb70eae..98cb4c50617afe 100644
--- a/src/libraries/System.IO.Compression/src/System.IO.Compression.csproj
+++ b/src/libraries/System.IO.Compression/src/System.IO.Compression.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -50,7 +50,7 @@
              Link="Common\Interop\Windows\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\IO\Compression\ZipArchiveEntry.Unix.cs" />
     <Compile Include="$(CommonPath)System\IO\Compression\ZipArchiveEntryConstants.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
diff --git a/src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj b/src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj
index 15afc84fa1c2f3..2598f311d40bb3 100644
--- a/src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj
+++ b/src/libraries/System.IO.Compression/tests/System.IO.Compression.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
   </PropertyGroup>
@@ -44,7 +44,7 @@
     <Compile Include="$(CommonPath)System\Net\MultiArrayBuffer.cs" Link="ProductionCode\Common\System\Net\MultiArrayBuffer.cs" />
     <Compile Include="$(CommonPath)System\Net\StreamBuffer.cs" Link="ProductionCode\Common\System\Net\StreamBuffer.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="ZipArchive\zip_CreateTests.Unix.cs" />
   </ItemGroup>
 
diff --git a/src/libraries/System.IO.FileSystem.DriveInfo/src/System.IO.FileSystem.DriveInfo.csproj b/src/libraries/System.IO.FileSystem.DriveInfo/src/System.IO.FileSystem.DriveInfo.csproj
index 61225e58e8a9b8..43823c8111daa1 100644
--- a/src/libraries/System.IO.FileSystem.DriveInfo/src/System.IO.FileSystem.DriveInfo.csproj
+++ b/src/libraries/System.IO.FileSystem.DriveInfo/src/System.IO.FileSystem.DriveInfo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System\IO\DriveInfo.cs" />
@@ -52,7 +52,7 @@
     <Compile Include="$(CoreLibSharedDir)System\IO\DriveInfoInternal.Windows.cs"
              Link="Common\System\IO\DriveInfoInternal.Windows.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\IO\DriveInfo.UnixOrDefault.cs" />
     <Compile Include="System\IO\DriveInfo.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
diff --git a/src/libraries/System.IO.FileSystem.DriveInfo/tests/System.IO.FileSystem.DriveInfo.Tests.csproj b/src/libraries/System.IO.FileSystem.DriveInfo/tests/System.IO.FileSystem.DriveInfo.Tests.csproj
index 00d1afd3c94116..cc4756c4483abe 100644
--- a/src/libraries/System.IO.FileSystem.DriveInfo/tests/System.IO.FileSystem.DriveInfo.Tests.csproj
+++ b/src/libraries/System.IO.FileSystem.DriveInfo/tests/System.IO.FileSystem.DriveInfo.Tests.csproj
@@ -1,9 +1,9 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="DriveInfo.Unix.Tests.cs" Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'" />
+    <Compile Include="DriveInfo.Unix.Tests.cs" Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'" />
     <Compile Include="DriveInfo.Windows.Tests.cs" Condition="'$(TargetPlatformIdentifier)' == 'windows'" />
     <Compile Include="VirtualDrives.Windows.Tests.cs" Condition="'$(TargetPlatformIdentifier)' == 'windows'" />
     <Compile Include="$(CommonTestPath)System\IO\VirtualDriveHelper.Windows.cs" Link="Common\System\IO\VirtualDriveHelper.Windows.cs" Condition="'$(TargetPlatformIdentifier)' == 'windows'" />
diff --git a/src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj b/src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj
index 469005b661d886..15b70f231a8298 100644
--- a/src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj
+++ b/src/libraries/System.IO.FileSystem.Watcher/src/System.IO.FileSystem.Watcher.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -68,7 +68,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.PathConf.cs"
              Link="Common\Interop\Unix\Interop.PathConf.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="System\IO\FileSystemWatcher.Linux.cs" />
     <Compile Include="$(CommonPath)Interop\Linux\System.Native\Interop.INotify.cs"
              Link="Common\Interop\Linux\Interop.inotify.cs" />
@@ -79,7 +79,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.Stat.cs"
              Link="Common\Interop\Unix\Interop.Stat.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'MacCatalyst'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'maccatalyst'">
     <Compile Include="System\IO\FileSystemWatcher.OSX.cs" />
     <Compile Include="$(CoreLibSharedDir)System\IO\FileSystem.Exists.Unix.cs"
              Link="System\IO\FileSystem.Exists.Unix.cs" />
diff --git a/src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj b/src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj
index 1246c914ab81d2..402b0b9da58f5b 100644
--- a/src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj
+++ b/src/libraries/System.IO.FileSystem.Watcher/tests/System.IO.FileSystem.Watcher.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-FreeBSD</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-freebsd</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser' or '$(TargetOS)' == 'iOSSimulator' or '$(TargetOS)' == 'iOS' or '$(TargetOS)' == 'tvOSSimulator' or '$(TargetOS)' == 'tvOS'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
@@ -56,7 +56,7 @@
     <Compile Include="$(CommonPath)System\IO\PathInternal.Unix.cs"
              Link="Common\System\IO\PathInternal.Unix.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="FileSystemWatcher.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
diff --git a/src/libraries/System.IO.FileSystem/tests/DisabledFileLockingTests/System.IO.FileSystem.DisabledFileLocking.Tests.csproj b/src/libraries/System.IO.FileSystem/tests/DisabledFileLockingTests/System.IO.FileSystem.DisabledFileLocking.Tests.csproj
index e8deebe6fb9f72..2ade72e35e2ca6 100644
--- a/src/libraries/System.IO.FileSystem/tests/DisabledFileLockingTests/System.IO.FileSystem.DisabledFileLocking.Tests.csproj
+++ b/src/libraries/System.IO.FileSystem/tests/DisabledFileLockingTests/System.IO.FileSystem.DisabledFileLocking.Tests.csproj
@@ -4,7 +4,7 @@
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
     <!-- file locking can't be disabled on Windows -->
-    <TargetFramework>$(NetCoreAppCurrent)-Unix</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-unix</TargetFramework>
 
     <WasmXHarnessMonoArgs>--working-dir=/test-dir</WasmXHarnessMonoArgs>
   </PropertyGroup>
diff --git a/src/libraries/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj b/src/libraries/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
index 0cc7805d4fd4be..fa31f6979a533f 100644
--- a/src/libraries/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
+++ b/src/libraries/System.IO.FileSystem/tests/System.IO.FileSystem.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
 
     <WasmXHarnessMonoArgs>--working-dir=/test-dir</WasmXHarnessMonoArgs>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
@@ -81,7 +81,7 @@
     <Compile Include="RandomAccess\WriteGather.cs" />
     <Compile Include="RandomAccess\WriteGatherAsync.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="FileSystemTest.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="FileStream\ctor_options.Unix.cs" />
@@ -117,7 +117,7 @@
     <ProjectReference Include="$(LibrariesProjectRoot)System.ServiceProcess.ServiceController\src\System.ServiceProcess.ServiceController.csproj" />
     <ProjectReference Include="$(LibrariesProjectRoot)System.IO.FileSystem.AccessControl\src\System.IO.FileSystem.AccessControl.csproj" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="FileSystemTest.Browser.cs" />
     <Compile Include="FileStream\ctor_options.Browser.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.IO.IsolatedStorage/src/System.IO.IsolatedStorage.csproj b/src/libraries/System.IO.IsolatedStorage/src/System.IO.IsolatedStorage.csproj
index 2309a8c007ab3f..e9502a92ac76ee 100644
--- a/src/libraries/System.IO.IsolatedStorage/src/System.IO.IsolatedStorage.csproj
+++ b/src/libraries/System.IO.IsolatedStorage/src/System.IO.IsolatedStorage.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -19,11 +19,11 @@
     <Compile Include="$(CommonPath)System\Security\IdentityHelper.cs"
              Link="Common\System\Security\IdentityHelper.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="System\IO\IsolatedStorage\Helper.AnyMobile.cs" />
     <Compile Include="System\IO\IsolatedStorage\IsolatedStorageFile.AnyMobile.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Android' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'MacCatalyst' and '$(TargetPlatformIdentifier)' != 'tvOS' and '$(TargetPlatformIdentifier)' != ''">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'android' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'maccatalyst' and '$(TargetPlatformIdentifier)' != 'tvos' and '$(TargetPlatformIdentifier)' != ''">
     <Compile Include="System\IO\IsolatedStorage\Helper.NonMobile.cs" />
     <Compile Include="System\IO\IsolatedStorage\IsolatedStorageFile.NonMobile.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.IO.IsolatedStorage/tests/System.IO.IsolatedStorage.Tests.csproj b/src/libraries/System.IO.IsolatedStorage/tests/System.IO.IsolatedStorage.Tests.csproj
index 0410513c46ceb1..9c9233c1d3c2de 100644
--- a/src/libraries/System.IO.IsolatedStorage/tests/System.IO.IsolatedStorage.Tests.csproj
+++ b/src/libraries/System.IO.IsolatedStorage/tests/System.IO.IsolatedStorage.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Android</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-android</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
   </PropertyGroup>
   <ItemGroup>
@@ -53,11 +53,11 @@
     <Compile Include="System\IO\IsolatedStorage\TestHelper.cs" />
     <Compile Include="System\IO\IsolatedStorage\RemoveTests.cs" />
   </ItemGroup>
-   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="..\src\System\IO\IsolatedStorage\Helper.AnyMobile.cs" />
     <Compile Include="System\IO\IsolatedStorage\TestHelper.AnyMobile.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Android' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'MacCatalyst' and '$(TargetPlatformIdentifier)' != 'tvOS' and '$(TargetPlatformIdentifier)' != ''">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'android' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'maccatalyst' and '$(TargetPlatformIdentifier)' != 'tvos' and '$(TargetPlatformIdentifier)' != ''">
     <Compile Include="..\src\System\IO\IsolatedStorage\Helper.NonMobile.cs" />
     <Compile Include="System\IO\IsolatedStorage\TestHelper.NonMobile.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.IO.MemoryMappedFiles/src/System.IO.MemoryMappedFiles.csproj b/src/libraries/System.IO.MemoryMappedFiles/src/System.IO.MemoryMappedFiles.csproj
index 9be9a376620fd2..c2eae8e5d3baef 100644
--- a/src/libraries/System.IO.MemoryMappedFiles/src/System.IO.MemoryMappedFiles.csproj
+++ b/src/libraries/System.IO.MemoryMappedFiles/src/System.IO.MemoryMappedFiles.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -80,7 +80,7 @@
     <Compile Include="System\IO\MemoryMappedFiles\MemoryMappedFile.Windows.cs" />
     <Compile Include="System\IO\MemoryMappedFiles\MemoryMappedView.Windows.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser' ">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser' ">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"
diff --git a/src/libraries/System.IO.MemoryMappedFiles/tests/System.IO.MemoryMappedFiles.Tests.csproj b/src/libraries/System.IO.MemoryMappedFiles/tests/System.IO.MemoryMappedFiles.Tests.csproj
index ef44754372ef71..7905e969060b98 100644
--- a/src/libraries/System.IO.MemoryMappedFiles/tests/System.IO.MemoryMappedFiles.Tests.csproj
+++ b/src/libraries/System.IO.MemoryMappedFiles/tests/System.IO.MemoryMappedFiles.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <ItemGroup>
@@ -18,7 +18,7 @@
     <Compile Include="MemoryMappedViewStream.Tests.cs" />
     <Compile Include="MemoryMappedViewAccessor.Tests.cs" />
     <Compile Include="MemoryMappedFilesTestsBase.cs" />
-    <Compile Include="MemoryMappedFilesTestsBase.Unix.cs" Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'" />
+    <Compile Include="MemoryMappedFilesTestsBase.Unix.cs" Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'" />
     <Compile Include="MemoryMappedFilesTestsBase.Windows.cs" Condition="'$(TargetPlatformIdentifier)' == 'windows'" />
     <Compile Include="$(CommonTestPath)System\IO\TempFile.cs" Link="Common\System\IO\TempFile.cs" />
     <Compile Include="SafeMemoryMappedViewHandleTests.cs" />
diff --git a/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj b/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
index b0956d6ba7bf31..8f50a32a09e67b 100644
--- a/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
+++ b/src/libraries/System.IO.Pipes/src/System.IO.Pipes.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
@@ -125,7 +125,7 @@
     <Compile Include="System\IO\Pipes\PipeStream.Windows.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="Microsoft\Win32\SafeHandles\SafePipeHandle.Unix.cs" />
     <Compile Include="System\IO\Pipes\AnonymousPipeServerStream.Unix.cs" />
     <Compile Include="System\IO\Pipes\NamedPipeClientStream.Unix.cs" />
@@ -190,7 +190,7 @@
     <Reference Include="System.Threading.ThreadPool" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Reference Include="Microsoft.Win32.Primitives" />
     <Reference Include="System.Net.Primitives" />
     <Reference Include="System.Net.Sockets" />
diff --git a/src/libraries/System.IO.Pipes/tests/System.IO.Pipes.Tests.csproj b/src/libraries/System.IO.Pipes/tests/System.IO.Pipes.Tests.csproj
index 44bb64719df7f1..83ace70b92702e 100644
--- a/src/libraries/System.IO.Pipes/tests/System.IO.Pipes.Tests.csproj
+++ b/src/libraries/System.IO.Pipes/tests/System.IO.Pipes.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
@@ -36,7 +36,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\Kernel32\Interop.GetNamedPipeHandleState.cs" Link="Common\Interop\Windows\Interop.GetNamedPipeHandleState.cs" />
     <Compile Include="$(CommonPath)Interop\Windows\Kernel32\Interop.MaxLengths.cs" Link="Common\Interop\Windows\Interop.MaxLengths.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="NamedPipeTests\NamedPipeTest.CurrentUserOnly.Unix.cs" />
     <Compile Include="NamedPipeTests\NamedPipeTest.UnixDomainSockets.cs" />
     <Compile Include="NamedPipeTests\NamedPipeTest.RunAsClient.Unix.cs" />
diff --git a/src/libraries/System.IO.Ports/src/System.IO.Ports.csproj b/src/libraries/System.IO.Ports/src/System.IO.Ports.csproj
index 28e0eabd867f8f..5797c2c5affb18 100644
--- a/src/libraries/System.IO.Ports/src/System.IO.Ports.csproj
+++ b/src/libraries/System.IO.Ports/src/System.IO.Ports.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-Unix;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-Unix;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-windows;$(NetCoreAppPrevious)-unix;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-windows;$(NetCoreAppMinimum)-unix;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DefineConstants>$(DefineConstants);SERIAL_PORTS</DefineConstants>
     <IncludeDllSafeSearchPathAttribute>true</IncludeDllSafeSearchPathAttribute>
@@ -122,7 +122,7 @@ System.IO.Ports.SerialPort</PackageDescription>
              Link="Common\Interop\Windows\Kernel32\Interop.FileOperations.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\IO\Ports\SafeSerialDeviceHandle.Unix.cs" />
     <Compile Include="System\IO\Ports\SerialPort.Unix.cs" />
     <Compile Include="System\IO\Ports\SerialStream.Unix.cs" />
diff --git a/src/libraries/System.IO.Ports/tests/System.IO.Ports.Tests.csproj b/src/libraries/System.IO.Ports/tests/System.IO.Ports.Tests.csproj
index 9a1592778a7dcc..a84a74343b0ae4 100644
--- a/src/libraries/System.IO.Ports/tests/System.IO.Ports.Tests.csproj
+++ b/src/libraries/System.IO.Ports/tests/System.IO.Ports.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-FreeBSD;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-freebsd;$(NetFrameworkMinimum)</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="AssemblyInfo.cs" />
diff --git a/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj b/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
index ce93213d3a10fe..2b41355f21462f 100644
--- a/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
+++ b/src/libraries/System.Linq.Expressions/src/System.Linq.Expressions.csproj
@@ -1,20 +1,20 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-MacCatalyst</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-maccatalyst</TargetFrameworks>
     <IsInterpreting>false</IsInterpreting>
     <DefineConstants> $(DefineConstants);FEATURE_FAST_CREATE</DefineConstants>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <IsInterpreting Condition="'$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst'">true</IsInterpreting>
+    <IsInterpreting Condition="'$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos' or '$(TargetPlatformIdentifier)' == 'maccatalyst'">true</IsInterpreting>
     <ILLinkSubstitutionsLibraryBuildXml Condition="'$(IsInterpreting)' == 'true'">ILLink\ILLink.Substitutions.IsInterpreting.LibraryBuild.xml</ILLinkSubstitutionsLibraryBuildXml>
     <!--
       Disable constant propagation so that methods referenced from ILLink.Substitutions.xml don't get inlined
       with a wrong value at library build time and the substitution can still be selected at publish time.
       For iOS/tvOS/Catalyst we prefer smaller size by default, so keep constprop enabled to get rid of the expression compiler.
     -->
-    <ILLinkDisableIPConstProp Condition="'$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'tvOS' and '$(TargetPlatformIdentifier)' != 'MacCatalyst'">true</ILLinkDisableIPConstProp>
+    <ILLinkDisableIPConstProp Condition="'$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'tvos' and '$(TargetPlatformIdentifier)' != 'maccatalyst'">true</ILLinkDisableIPConstProp>
   </PropertyGroup>
   <ItemGroup>
     <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.xml" />
diff --git a/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj b/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
index c0e8f7d6c9fe61..481d04cc820ac7 100644
--- a/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
+++ b/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-MacCatalyst</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-maccatalyst</TargetFrameworks>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/libraries/System.Linq/src/System.Linq.csproj b/src/libraries/System.Linq/src/System.Linq.csproj
index e0509ff215fd85..0babce85894de8 100644
--- a/src/libraries/System.Linq/src/System.Linq.csproj
+++ b/src/libraries/System.Linq/src/System.Linq.csproj
@@ -1,11 +1,11 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <OptimizeForSize Condition="'$(TargetPlatformIdentifier)' == 'Browser' or '$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</OptimizeForSize>
+    <OptimizeForSize Condition="'$(TargetPlatformIdentifier)' == 'browser' or '$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</OptimizeForSize>
   </PropertyGroup>
   <ItemGroup Condition="'$(OptimizeForSize)' == true">
     <Compile Include="System\Linq\Enumerable.SizeOpt.cs" />
diff --git a/src/libraries/System.Net.Http/src/System.Net.Http.csproj b/src/libraries/System.Net.Http/src/System.Net.Http.csproj
index 3f66b5f729f363..ff5bc237b88f59 100644
--- a/src/libraries/System.Net.Http/src/System.Net.Http.csproj
+++ b/src/libraries/System.Net.Http/src/System.Net.Http.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DefineConstants>$(DefineConstants);HTTP_DLL</DefineConstants>
     <EnablePreviewFeatures>true</EnablePreviewFeatures>
@@ -9,21 +9,21 @@
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.PlatformNotSupported_NetHttp</GeneratePlatformNotSupportedAssemblyMessage>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst'">$(DefineConstants);SYSNETHTTP_NO_OPENSSL</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS'">$(DefineConstants);TARGET_MOBILE</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Android'">$(DefineConstants);TARGET_ANDROID</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'iOS'">$(DefineConstants);TARGET_IOS</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'MacCatalyst'">$(DefineConstants);TARGET_MACCATALYST</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'tvOS'">$(DefineConstants);TARGET_TVOS</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Browser'">$(DefineConstants);TARGET_BROWSER</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos' or '$(TargetPlatformIdentifier)' == 'maccatalyst'">$(DefineConstants);SYSNETHTTP_NO_OPENSSL</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos'">$(DefineConstants);TARGET_MOBILE</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'android'">$(DefineConstants);TARGET_ANDROID</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'ios'">$(DefineConstants);TARGET_IOS</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'maccatalyst'">$(DefineConstants);TARGET_MACCATALYST</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'tvos'">$(DefineConstants);TARGET_TVOS</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'browser'">$(DefineConstants);TARGET_BROWSER</DefineConstants>
     <!-- ILLinker settings -->
     <ILLinkDirectory>$(MSBuildThisFileDirectory)ILLink\</ILLinkDirectory>
   </PropertyGroup>
   <ItemGroup>
     <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.xml" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS' or '$(TargetPlatformIdentifier)' == 'Browser'">
-    <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.mobile.xml" Condition="'$(TargetPlatformIdentifier)' != 'Browser'" />
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos' or '$(TargetPlatformIdentifier)' == 'browser'">
+    <ILLinkSubstitutionsXmls Include="$(ILLinkDirectory)ILLink.Substitutions.mobile.xml" Condition="'$(TargetPlatformIdentifier)' != 'browser'" />
     <ILLinkSuppressionsXmls Include="$(ILLinkDirectory)ILLink.Suppressions.Mobile.LibraryBuild.xml" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != ''">
@@ -44,11 +44,11 @@
     <Compile Include="System\Net\Http\Headers\KnownHeaders.cs" />
     <Compile Include="System\Net\Http\HttpBaseStream.cs" />
     <Compile Include="System\Net\Http\HttpClient.cs" />
-    <Compile Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS'"
+    <Compile Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos'"
              Include="System\Net\Http\HttpClientHandler.AnyMobile.cs" />
-    <Compile Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'MacCatalyst' or '$(TargetPlatformIdentifier)' == 'tvOS'"
+    <Compile Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'maccatalyst' or '$(TargetPlatformIdentifier)' == 'tvos'"
              Include="System\Net\Http\HttpClientHandler.AnyMobile.InvokeNativeHandler.cs" />
-    <Compile Condition="'$(TargetPlatformIdentifier)' != 'Android' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'MacCatalyst' and '$(TargetPlatformIdentifier)' != 'tvOS'"
+    <Compile Condition="'$(TargetPlatformIdentifier)' != 'android' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'maccatalyst' and '$(TargetPlatformIdentifier)' != 'tvos'"
              Include="System\Net\Http\HttpClientHandler.cs" />
     <Compile Include="System\Net\Http\HttpCompletionOption.cs" />
     <Compile Include="System\Net\Http\HttpContent.cs" />
@@ -155,7 +155,7 @@
              Link="Common\System\Text\ValueStringBuilder.AppendSpanFormattable.cs" />
   </ItemGroup>
   <!-- SocketsHttpHandler implementation -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="System\Net\Http\HttpHandlerDefaults.cs" />
     <Compile Include="System\Net\Http\HttpMethod.Http3.cs" />
     <Compile Include="System\Net\Http\Headers\AltSvcHeaderParser.cs" />
@@ -303,16 +303,16 @@
     </Compile>
   </ItemGroup>
   <!-- SocketsHttpHandler platform parts -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="System\Net\Http\SocketsHttpHandler\HttpEnvironmentProxy.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\HttpEnvironmentProxy.Unix.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\CurrentUserIdentityProvider.Unix.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser' and '$(TargetPlatformIdentifier)' != 'OSX' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser' and '$(TargetPlatformIdentifier)' != 'osx' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'tvos'">
     <Compile Include="System\Net\Http\SocketsHttpHandler\HttpNoProxy.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Unix.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="System\Net\Http\SocketsHttpHandler\SystemProxyInfo.OSX.cs" />
     <Compile Include="System\Net\Http\SocketsHttpHandler\MacProxy.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.CoreFoundation.cs"
@@ -384,7 +384,7 @@
     <Compile Include="$(CommonPath)System\Threading\Tasks\TaskToApm.cs"
              Link="Common\System\Threading\Tasks\TaskToApm.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="$(CommonPath)System\StrongToWeakReference.cs"
              Link="Common\Interop\Unix\StrongToWeakReference.cs" />
     <Compile Include="$(CommonPath)System\Net\SecurityProtocol.cs"
@@ -412,11 +412,11 @@
     <Compile Include="$(CommonPath)System\Threading\Tasks\TaskToApm.cs"
              Link="Common\System\Threading\Tasks\TaskToApm.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser' and '$(TargetPlatformIdentifier)' != 'OSX' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser' and '$(TargetPlatformIdentifier)' != 'osx' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'tvos'">
     <Compile Include="$(CommonPath)Interop\Unix\System.Security.Cryptography.Native\Interop.Initialization.cs"
              Link="Common\Interop\Unix\System.Security.Cryptography.Native\Interop.Initialization.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)\System\StringExtensions.cs"
              Link="Common\System\StringExtensions.cs" />
     <Compile Include="$(CommonPath)\System\Net\HttpStatusDescription.cs"
@@ -462,11 +462,11 @@
     <Reference Include="System.Threading.ThreadPool" />
     <Reference Include="System.IO.Compression.Brotli" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Reference Include="System.Diagnostics.StackTrace" />
     <Reference Include="System.Security.Cryptography" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\gen\JSImportGenerator\JSImportGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     <Reference Include="System.Runtime.InteropServices.JavaScript" />
   </ItemGroup>
diff --git a/src/libraries/System.Net.Http/tests/EnterpriseTests/System.Net.Http.Enterprise.Tests.csproj b/src/libraries/System.Net.Http/tests/EnterpriseTests/System.Net.Http.Enterprise.Tests.csproj
index 4af21d65d63e26..75b09f1487abe9 100644
--- a/src/libraries/System.Net.Http/tests/EnterpriseTests/System.Net.Http.Enterprise.Tests.csproj
+++ b/src/libraries/System.Net.Http/tests/EnterpriseTests/System.Net.Http.Enterprise.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Net.Http/tests/FunctionalTests/System.Net.Http.Functional.Tests.csproj b/src/libraries/System.Net.Http/tests/FunctionalTests/System.Net.Http.Functional.Tests.csproj
index 416a0fae6a17fc..f34791454bcf8e 100644
--- a/src/libraries/System.Net.Http/tests/FunctionalTests/System.Net.Http.Functional.Tests.csproj
+++ b/src/libraries/System.Net.Http/tests/FunctionalTests/System.Net.Http.Functional.Tests.csproj
@@ -6,7 +6,7 @@
     <DefineConstants>$(DefineConstants);SYSNETHTTP_NO_OPENSSL;HTTP3</DefineConstants>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
     <EnablePreviewFeatures>true</EnablePreviewFeatures>
     <!-- the res/xml/network_security_config.xml file comes from the System.Net.TestData package -->
@@ -18,7 +18,7 @@
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'windows'">$(DefineConstants);TargetsWindows</DefineConstants>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Browser'">$(DefineConstants);TARGETS_BROWSER</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'browser'">$(DefineConstants);TARGETS_BROWSER</DefineConstants>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(TargetOS)' == 'Browser'">
@@ -178,7 +178,7 @@
     <Compile Include="HttpClientHandlerTestBase.SocketsHttpHandler.cs" />
     <Compile Include="DiagnosticsTests.cs" />
     <Compile Include="HttpClientTest.cs" />
-    <Compile Include="$(CommonTestPath)System\Net\Http\HttpClientEKUTest.cs" Condition="'$(TargetPlatformIdentifier)' != 'Browser'"
+    <Compile Include="$(CommonTestPath)System\Net\Http\HttpClientEKUTest.cs" Condition="'$(TargetPlatformIdentifier)' != 'browser'"
              Link="Common\System\Net\Http\HttpClientEKUTest.cs" />
     <Compile Include="$(CommonTestPath)System\Net\Http\HttpClient.SelectedSitesTest.cs"
              Link="Common\System\Net\Http\HttpClient.SelectedSitesTest.cs" />
@@ -230,12 +230,12 @@
     <Compile Include="ImpersonatedAuthTests.cs" />
   </ItemGroup>
   <!-- Linux specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs"
              Link="Common\Interop\Linux\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- OSX specific files -->
-  <ItemGroup Condition=" '$(TargetPlatformIdentifier)' == 'OSX' ">
+  <ItemGroup Condition=" '$(TargetPlatformIdentifier)' == 'osx' ">
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs"
              Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Net.Http/tests/UnitTests/System.Net.Http.Unit.Tests.csproj b/src/libraries/System.Net.Http/tests/UnitTests/System.Net.Http.Unit.Tests.csproj
index 85139c5391ff85..0ce09550fab2b0 100644
--- a/src/libraries/System.Net.Http/tests/UnitTests/System.Net.Http.Unit.Tests.csproj
+++ b/src/libraries/System.Net.Http/tests/UnitTests/System.Net.Http.Unit.Tests.csproj
@@ -3,7 +3,7 @@
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-MacCatalyst;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Android</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-maccatalyst;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-android</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <!-- Do not reference these assemblies from the TargetingPack since we are building part of the source code for tests. -->
@@ -246,18 +246,18 @@
              Link="ProductionCode\System\Net\Http\SocketsHttpHandler\HttpUtilities.cs" />
     <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.cs"
              Link="ProductionCode\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.cs" />
-    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.OSX.cs" Condition=" '$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'"
+    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.OSX.cs" Condition=" '$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'"
              Link="ProductionCode\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.OSX.cs" />
-    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Unix.cs" Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'OSX' and '$(TargetPlatformIdentifier)' != 'iOS' and '$(TargetPlatformIdentifier)' != 'tvOS'"
+    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Unix.cs" Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'osx' and '$(TargetPlatformIdentifier)' != 'ios' and '$(TargetPlatformIdentifier)' != 'tvos'"
              Link="ProductionCode\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Unix.cs" />
-    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Windows.cs" Condition=" '$(TargetPlatformIdentifier)' == 'windows' "
+    <Compile Include="..\..\src\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Windows.cs" Condition="'$(TargetPlatformIdentifier)' == 'windows'"
              Link="ProductionCode\System\Net\Http\SocketsHttpHandler\SystemProxyInfo.Windows.cs" />
     <Compile Include="$(CommonPath)System\Net\Http\HttpHandlerDefaults.cs"
              Link="ProductionCode\System\Net\Http\HttpHandlerDefaults.cs" />
     <Compile Include="DigestAuthenticationTests.cs" />
     <Compile Include="Fakes\HttpClientHandler.cs" />
     <Compile Include="Fakes\HttpTelemetry.cs" />
-    <Compile Include="Fakes\MacProxy.cs" Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'" />
+    <Compile Include="Fakes\MacProxy.cs" Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'" />
     <Compile Include="Headers\AltSvcHeaderParserTest.cs" />
     <Compile Include="Headers\AuthenticationHeaderValueTest.cs" />
     <Compile Include="Headers\ByteArrayHeaderParserTest.cs" />
diff --git a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
index a72b0e81ef495d..983282a6341db3 100644
--- a/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
+++ b/src/libraries/System.Net.HttpListener/src/System.Net.HttpListener.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <ForceManagedImplementation>false</ForceManagedImplementation>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
     <EnableAOTAnalyzer>true</EnableAOTAnalyzer>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
@@ -251,7 +251,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\SspiCli\SSPIWrapper.cs"
              Link="Common\Interop\Windows\SspiCli\SSPIWrapper.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(ForceManagedImplementation)' == 'true'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(ForceManagedImplementation)' == 'true'">
     <Compile Include="System\Net\Managed\HttpEndPointListener.cs" />
     <Compile Include="System\Net\Managed\HttpEndPointManager.cs" />
     <Compile Include="System\Net\Managed\HttpConnection.cs" />
diff --git a/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj b/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
index ff51965c789584..823a75101cfd98 100644
--- a/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
+++ b/src/libraries/System.Net.HttpListener/tests/System.Net.HttpListener.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Net.Mail/src/System.Net.Mail.csproj b/src/libraries/System.Net.Mail/src/System.Net.Mail.csproj
index 5d2ce4cc28099d..7d1afb2d61aa70 100644
--- a/src/libraries/System.Net.Mail/src/System.Net.Mail.csproj
+++ b/src/libraries/System.Net.Mail/src/System.Net.Mail.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -78,12 +78,12 @@
              Link="Common\System\HexConverter.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\Net\Mail\SmtpClient.Browser.cs" />
   </ItemGroup>
 
   <!-- Non Browser specific files - internal and security -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="System\Net\Mail\SmtpClient.cs" />
     <Compile Include="System\Net\Mail\ISmtpAuthenticationModule.cs" />
     <Compile Include="System\Net\Mail\SmtpAuthenticationManager.cs" />
@@ -119,7 +119,7 @@
   </ItemGroup>
 
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="$(CommonPath)System\Net\ContextAwareResult.Unix.cs"
              Link="Common\System\Net\ContextAwareResult.Unix.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Net.Mail/tests/Functional/System.Net.Mail.Functional.Tests.csproj b/src/libraries/System.Net.Mail/tests/Functional/System.Net.Mail.Functional.Tests.csproj
index 351ce98344883d..b2ce00275613a5 100644
--- a/src/libraries/System.Net.Mail/tests/Functional/System.Net.Mail.Functional.Tests.csproj
+++ b/src/libraries/System.Net.Mail/tests/Functional/System.Net.Mail.Functional.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-Android</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-android</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <EnablePreviewFeatures>true</EnablePreviewFeatures>
@@ -32,7 +32,7 @@
              Link="Common\System\Threading\Tasks\TaskTimeoutExtensions.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="SmtpClientTest.cs" />
     <Compile Include="SmtpClientCredentialsTest.cs" />
     <Compile Include="LoggingTest.cs" />
@@ -52,7 +52,7 @@
   </ItemGroup>
 
   <!-- Unix specific files (NT Authentication) -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Net.Security.Native\Interop.NetSecurityNative.IsNtlmInstalled.cs"
diff --git a/src/libraries/System.Net.Mail/tests/Unit/System.Net.Mail.Unit.Tests.csproj b/src/libraries/System.Net.Mail/tests/Unit/System.Net.Mail.Unit.Tests.csproj
index 0fbb5d7c49728c..e7eeed8be58c97 100644
--- a/src/libraries/System.Net.Mail/tests/Unit/System.Net.Mail.Unit.Tests.csproj
+++ b/src/libraries/System.Net.Mail/tests/Unit/System.Net.Mail.Unit.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <ItemGroup>
@@ -18,7 +18,7 @@
     <Compile Include="MessageTests\MessageHeaderBehaviorTest.cs" />
     <Compile Include="MessageTests\ReplyToListTest.cs" />
     <Compile Include="QuotedPrintableStreamTest.cs" />
-    <Compile Include="SmtpConnectionTests\EhloParseExtensionsTest.cs" Condition="'$(TargetPlatformIdentifier)' != 'Browser'" />
+    <Compile Include="SmtpConnectionTests\EhloParseExtensionsTest.cs" Condition="'$(TargetPlatformIdentifier)' != 'browser'" />
     <Compile Include="SmtpDateTimeTest.cs" />
     <Compile Include="WriteStateInfoTest.cs" />
   </ItemGroup>
@@ -147,7 +147,7 @@
              Link="Common\System\HexConverter.cs" />
   </ItemGroup>
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="$(CommonPath)System\Net\ContextAwareResult.Unix.cs"
              Link="Common\System\Net\ContextAwareResult.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
@@ -160,7 +160,7 @@
   </ItemGroup>
 
   <!-- Non Browser specific files - internal and security -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="..\..\src\System\Net\Mail\SmtpLoginAuthenticationModule.cs"
              Link="ProductionCode\SmtpLoginAuthenticationModule.cs" />
     <Compile Include="..\..\src\System\Net\Mail\SmtpNegotiateAuthenticationModule.cs"
diff --git a/src/libraries/System.Net.NameResolution/src/System.Net.NameResolution.csproj b/src/libraries/System.Net.NameResolution/src/System.Net.NameResolution.csproj
index 37d30c08474e6d..127119d3ea3082 100644
--- a/src/libraries/System.Net.NameResolution/src/System.Net.NameResolution.csproj
+++ b/src/libraries/System.Net.NameResolution/src/System.Net.NameResolution.csproj
@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == 'Browser' or '$(TargetPlatformIdentifier)' == ''">SR.SystemNetNameResolution_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
-    <ApiExclusionListPath Condition="'$(TargetPlatformIdentifier)' == 'Browser'">ExcludeApiList.PNSE.Browser.txt</ApiExclusionListPath>
+    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == 'browser' or '$(TargetPlatformIdentifier)' == ''">SR.SystemNetNameResolution_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
+    <ApiExclusionListPath Condition="'$(TargetPlatformIdentifier)' == 'browser'">ExcludeApiList.PNSE.Browser.txt</ApiExclusionListPath>
   </PropertyGroup>
   <ItemGroup Condition="'$(GeneratePlatformNotSupportedAssemblyMessage)' == ''">
     <Compile Include="System\Net\Dns.cs" />
@@ -71,7 +71,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\WinSock\Interop.GetAddrInfoExW.cs"
              Link="Common\Interop\Windows\WinSock\Interop.GetAddrInfoExW.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\Net\NameResolutionPal.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\InteropIPAddressExtensions.Unix.cs"
              Link="Common\System\Net\InteropIPAddressExtensions.Unix.cs" />
@@ -98,7 +98,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.SocketAddress.cs"
              Link="Common\Interop\Unix\System.Native\Interop.SocketAddress.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\Net\Dns.Browser.cs" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Net.NameResolution/tests/FunctionalTests/System.Net.NameResolution.Functional.Tests.csproj b/src/libraries/System.Net.NameResolution/tests/FunctionalTests/System.Net.NameResolution.Functional.Tests.csproj
index f4588a2b4a1125..00baeb74700bc0 100644
--- a/src/libraries/System.Net.NameResolution/tests/FunctionalTests/System.Net.NameResolution.Functional.Tests.csproj
+++ b/src/libraries/System.Net.NameResolution/tests/FunctionalTests/System.Net.NameResolution.Functional.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EventSourceSupport Condition="'$(TestNativeAot)' == 'true'">true</EventSourceSupport>
diff --git a/src/libraries/System.Net.NameResolution/tests/PalTests/System.Net.NameResolution.Pal.Tests.csproj b/src/libraries/System.Net.NameResolution/tests/PalTests/System.Net.NameResolution.Pal.Tests.csproj
index 75e949f5bfc9e3..2993a98f6fb6c1 100644
--- a/src/libraries/System.Net.NameResolution/tests/PalTests/System.Net.NameResolution.Pal.Tests.csproj
+++ b/src/libraries/System.Net.NameResolution/tests/PalTests/System.Net.NameResolution.Pal.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
@@ -73,7 +73,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\WinSock\Interop.GetAddrInfoExW.cs"
              Link="Common\Interop\Windows\WinSock\Interop.GetAddrInfoExW.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)System\Net\SocketAddressPal.Unix.cs"
              Link="Common\System\Net\Internals\SocketAddressPal.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\InteropIPAddressExtensions.Unix.cs"
diff --git a/src/libraries/System.Net.NetworkInformation/src/System.Net.NetworkInformation.csproj b/src/libraries/System.Net.NetworkInformation/src/System.Net.NetworkInformation.csproj
index d36ad67504ed4f..a77945404a17cd 100644
--- a/src/libraries/System.Net.NetworkInformation/src/System.Net.NetworkInformation.csproj
+++ b/src/libraries/System.Net.NetworkInformation/src/System.Net.NetworkInformation.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -27,7 +27,7 @@
     <Compile Include="System\Net\NetworkInformation\MulticastIPAddressInformationCollection.cs" />
     <Compile Include="System\Net\NetworkInformation\NetBiosNodeType.cs" />
     <Compile Include="System\Net\NetworkInformation\NetEventSource.NetworkInformation.cs" />
-    <Compile Include="System\Net\NetworkInformation\NetworkAddressChange.cs" Condition="'$(TargetPlatformIdentifier)' != 'illumos' and '$(TargetPlatformIdentifier)' != 'Solaris'" />
+    <Compile Include="System\Net\NetworkInformation\NetworkAddressChange.cs" Condition="'$(TargetPlatformIdentifier)' != 'illumos' and '$(TargetPlatformIdentifier)' != 'solaris'" />
     <Compile Include="System\Net\NetworkInformation\NetworkAvailabilityEventArgs.cs" />
     <Compile Include="System\Net\NetworkInformation\NetworkChangeDelegates.cs" />
     <Compile Include="System\Net\NetworkInformation\NetworkInterface.cs" />
@@ -120,7 +120,7 @@
     <Compile Include="$(CommonPath)System\IO\RowConfigReader.cs" Link="Common\System\IO\RowConfigReader.cs" />
   </ItemGroup>
   <!-- Linux (other than Android) -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux'">
     <Compile Include="System\Net\NetworkInformation\ExceptionHelper.Linux.cs" />
     <Compile Include="System\Net\NetworkInformation\LinuxIcmpV4Statistics.cs" />
     <Compile Include="System\Net\NetworkInformation\LinuxIcmpV6Statistics.cs" />
@@ -146,7 +146,7 @@
     <Compile Include="$(CommonPath)Interop\Linux\Interop.LinuxNetDeviceFlags.cs" Link="Common\Interop\Linux\Interop.LinuxNetDeviceFlags.cs" />
   </ItemGroup>
   <!-- Android -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Android'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'android'">
     <Compile Include="System\Net\NetworkInformation\IPGlobalPropertiesPal.Android.cs" />
     <Compile Include="System\Net\NetworkInformation\AndroidIPGlobalProperties.cs" />
     <Compile Include="System\Net\NetworkInformation\AndroidIPGlobalStatistics.cs" />
@@ -157,7 +157,7 @@
     <Compile Include="System\Net\NetworkInformation\AndroidNetworkInterface.cs" />
   </ItemGroup>
   <!-- OSX -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS' or '$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos' or '$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="System\Net\NetworkInformation\IPGlobalPropertiesPal.Bsd.cs" />
     <Compile Include="System\Net\NetworkInformation\NetworkInterfacePal.Bsd.cs" />
     <Compile Include="System\Net\NetworkInformation\BsdIcmpV4Statistics.cs" />
@@ -176,7 +176,7 @@
     <Compile Include="$(CommonPath)Interop\BSD\System.Native\Interop.ProtocolStatistics.cs" Link="Common\Interop\BSD\System.Native\Interop.ProtocolStatistics.cs" />
     <Compile Include="$(CommonPath)Interop\BSD\System.Native\Interop.TcpConnectionInfo.cs" Link="Common\Interop\BSD\System.Native\Interop.TcpConnectionInfo.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">
     <Compile Include="System\Net\NetworkInformation\NetworkAddressChange.OSX.cs" />
     <!-- OSX Common -->
     <Compile Include="$(CommonPath)Interop\OSX\Interop.CoreFoundation.cs" Link="Common\Interop\OSX\Interop.CoreFoundation.cs" />
@@ -185,15 +185,15 @@
     <Compile Include="$(CommonPath)Interop\OSX\Interop.SystemConfiguration.cs" Link="Common\Interop\OSX\Interop.SystemConfiguration.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeCreateHandle.OSX.cs" Link="Common\Microsoft\Win32\SafeHandles\SafeCreateHandle.OSX.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="$(CommonPath)Interop\FreeBSD\Interop.Libraries.cs" Link="Common\Interop\FreeBSD\Interop.Libraries.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="System\Net\NetworkInformation\NetworkAddressChange.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.NetworkChange.cs" Link="Common\Interop\Unix\System.Native\Interop.NetworkChange.cs" />
   </ItemGroup>
   <!-- Unknown Unix -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'UnknownUnix' or '$(TargetPlatformIdentifier)' == 'illumos' or '$(TargetPlatformIdentifier)' == 'Solaris'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'illumos' or '$(TargetPlatformIdentifier)' == 'solaris'">
     <Compile Include="System\Net\NetworkInformation\IPGlobalPropertiesPal.UnknownUnix.cs" />
     <Compile Include="System\Net\NetworkInformation\NetworkInterfacePal.UnknownUnix.cs" />
     <Compile Include="System\Net\NetworkInformation\NetworkAddressChange.UnknownUnix.cs" />
diff --git a/src/libraries/System.Net.Ping/src/System.Net.Ping.csproj b/src/libraries/System.Net.Ping/src/System.Net.Ping.csproj
index c0efcdd6f322f3..16b84ae2ad5af6 100644
--- a/src/libraries/System.Net.Ping/src/System.Net.Ping.csproj
+++ b/src/libraries/System.Net.Ping/src/System.Net.Ping.csproj
@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.SystemNetPing_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
-    <IsApplePlatform Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</IsApplePlatform>
+    <IsApplePlatform Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</IsApplePlatform>
   </PropertyGroup>
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' != ''">
     <Compile Include="System\Net\NetworkInformation\IPStatus.cs" />
diff --git a/src/libraries/System.Net.Ping/tests/FunctionalTests/System.Net.Ping.Functional.Tests.csproj b/src/libraries/System.Net.Ping/tests/FunctionalTests/System.Net.Ping.Functional.Tests.csproj
index 0a068b65b7254b..b140512de99bb0 100644
--- a/src/libraries/System.Net.Ping/tests/FunctionalTests/System.Net.Ping.Functional.Tests.csproj
+++ b/src/libraries/System.Net.Ping/tests/FunctionalTests/System.Net.Ping.Functional.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
diff --git a/src/libraries/System.Net.Primitives/src/System.Net.Primitives.csproj b/src/libraries/System.Net.Primitives/src/System.Net.Primitives.csproj
index b77d6366c7a966..b051d509fd60ac 100644
--- a/src/libraries/System.Net.Primitives/src/System.Net.Primitives.csproj
+++ b/src/libraries/System.Net.Primitives/src/System.Net.Primitives.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <ILLinkKeepDepAttributes>false</ILLinkKeepDepAttributes> <!-- See comments in Cookie.cs -->
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
     <!-- SYSTEM_NET_PRIMITIVES_DLL is required to allow source-level code sharing for types defined within the
          System.Net.Internals namespace. -->
     <DefineConstants>$(DefineConstants);SYSTEM_NET_PRIMITIVES_DLL</DefineConstants>
@@ -113,7 +113,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\IpHlpApi\Interop.if_nametoindex.cs"
              Link="Common\Interop\Windows\IpHlpApi\Interop.if_nametoindex.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\Net\SocketException.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\SocketAddressPal.Unix.cs"
              Link="Common\System\Net\SocketAddressPal.Unix.cs" />
@@ -128,7 +128,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.SocketAddress.cs"
              Link="Common\Interop\Unix\System.Native\Interop.SocketAddress.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\HostInformationPal.Unix.cs"
              Link="Common\System\Net\NetworkInformation\HostInformationPal.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\InterfaceInfoPal.Unix.cs"
@@ -144,7 +144,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.InterfaceNameToIndex.cs"
              Link="Common\Interop\Unix\System.Native\Interop.InterfaceNameToIndex.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\HostInformationPal.Browser.cs"
              Link="Common\System\Net\NetworkInformation\HostInformationPal.Browser.cs" />
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\InterfaceInfoPal.Browser.cs"
diff --git a/src/libraries/System.Net.Primitives/tests/FunctionalTests/System.Net.Primitives.Functional.Tests.csproj b/src/libraries/System.Net.Primitives/tests/FunctionalTests/System.Net.Primitives.Functional.Tests.csproj
index d31b916f781f33..05ec279eaf2c38 100644
--- a/src/libraries/System.Net.Primitives/tests/FunctionalTests/System.Net.Primitives.Functional.Tests.csproj
+++ b/src/libraries/System.Net.Primitives/tests/FunctionalTests/System.Net.Primitives.Functional.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <EventSourceSupport>true</EventSourceSupport>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Net.Primitives/tests/PalTests/System.Net.Primitives.Pal.Tests.csproj b/src/libraries/System.Net.Primitives/tests/PalTests/System.Net.Primitives.Pal.Tests.csproj
index 01b3e14365783e..fde9a8ab0e3510 100644
--- a/src/libraries/System.Net.Primitives/tests/PalTests/System.Net.Primitives.Pal.Tests.csproj
+++ b/src/libraries/System.Net.Primitives/tests/PalTests/System.Net.Primitives.Pal.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <PropertyGroup>
@@ -79,7 +79,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\IpHlpApi\Interop.if_nametoindex.cs"
              Link="ProductionCode\Common\Interop\Windows\IpHlpApi\Interop.if_nametoindex.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="..\..\src\System\Net\SocketException.Unix.cs"
              Link="ProductionCode\System\Net\SocketException.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\SocketAddressPal.Unix.cs"
@@ -95,7 +95,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.SocketAddress.cs"
              Link="ProductionCode\Common\Interop\Unix\System.Native\Interop.SocketAddress.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\HostInformationPal.Unix.cs"
              Link="Common\System\Net\NetworkInformation\HostInformationPal.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\InterfaceInfoPal.Unix.cs"
@@ -111,7 +111,7 @@
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.InterfaceNameToIndex.cs"
              Link="Common\Interop\Unix\System.Native\Interop.InterfaceNameToIndex.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\HostInformationPal.Browser.cs"
              Link="Common\System\Net\NetworkInformation\HostInformationPal.Browser.cs" />
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\InterfaceInfoPal.Browser.cs"
diff --git a/src/libraries/System.Net.Primitives/tests/UnitTests/System.Net.Primitives.UnitTests.Tests.csproj b/src/libraries/System.Net.Primitives/tests/UnitTests/System.Net.Primitives.UnitTests.Tests.csproj
index 8cc3d0ff90fcb5..df7e660405802b 100644
--- a/src/libraries/System.Net.Primitives/tests/UnitTests/System.Net.Primitives.UnitTests.Tests.csproj
+++ b/src/libraries/System.Net.Primitives/tests/UnitTests/System.Net.Primitives.UnitTests.Tests.csproj
@@ -3,7 +3,7 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <NoWarn>169,649</NoWarn>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <PropertyGroup>
@@ -89,7 +89,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\Interop.Libraries.cs"
              Link="ProductionCode\Common\Interop\Windows\Interop.Libraries.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="..\..\src\System\Net\SocketException.Unix.cs"
              Link="ProductionCode\System\Net\SocketException.Unix.cs" />
     <Compile Include="$(CommonPath)System\Net\NetworkInformation\InterfaceInfoPal.Unix.cs"
diff --git a/src/libraries/System.Net.Quic/src/System.Net.Quic.csproj b/src/libraries/System.Net.Quic/src/System.Net.Quic.csproj
index 257af8dbb8808b..e93558c30f2c94 100644
--- a/src/libraries/System.Net.Quic/src/System.Net.Quic.csproj
+++ b/src/libraries/System.Net.Quic/src/System.Net.Quic.csproj
@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)</TargetFrameworks>
     <EnableAOTAnalyzer>true</EnableAOTAnalyzer>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'FreeBSD' or '$(TargetPlatformIdentifier)' == 'OSX'">$(DefineConstants);SOCKADDR_HAS_LENGTH</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'freebsd' or '$(TargetPlatformIdentifier)' == 'osx'">$(DefineConstants);SOCKADDR_HAS_LENGTH</DefineConstants>
     <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'windows'">$(DefineConstants);TARGET_WINDOWS</DefineConstants>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.SystemNetQuic_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
     <ApiExclusionListPath Condition="'$(TargetPlatformIdentifier)' == ''">ExcludeApiList.PNSE.txt</ApiExclusionListPath>
@@ -58,7 +58,7 @@
     <Compile Include="$(CommonPath)System\Net\SocketAddressPal.Windows.cs" Link="Common\System\Net\SocketAddressPal.Windows.cs" />
   </ItemGroup>
   <!-- Unix (OSX + Linux) specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'freebsd'">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs" Link="Common\Interop\Unix\Interop.Errors.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Security.Cryptography.Native\Interop.ASN1.cs" Link="Common\Interop\Unix\System.Security.Cryptography.Native\Interop.ASN1.cs" />
@@ -82,17 +82,17 @@
     <Compile Include="$(CommonPath)System\Net\SocketAddressPal.Unix.cs" Link="Common\System\Net\SocketAddressPal.Unix.cs" />
   </ItemGroup>
   <!-- Linux specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux'">
     <Compile Include="$(CommonPath)System\Net\Security\CertificateValidation.Unix.cs" Link="Common\System\Net\Security\CertificateValidation.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Linux\Interop.Libraries.cs" Link="Common\Interop\Linux\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- FreeBSD specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'FreeBSD' ">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'freebsd' ">
     <Compile Include="$(CommonPath)System\Net\Security\CertificateValidation.Unix.cs" Link="Common\System\Net\Security\CertificateValidation.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\FreeBSD\Interop.Libraries.cs" Link="Common\Interop\FreeBSD\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- OSX specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="$(CommonPath)System\Net\Security\CertificateValidation.OSX.cs" Link="Common\System\Net\Security\CertificateValidation.OSX.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.Libraries.cs" Link="Common\Interop\OSX\Interop.Libraries.cs" />
   </ItemGroup>
@@ -134,7 +134,7 @@
     <Reference Include="Microsoft.Win32.Registry" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Linux' or '$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'FreeBSD'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'linux' or '$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'freebsd'">
     <Reference Include="System.Diagnostics.StackTrace" Condition="'$(Configuration)' == 'Debug'" />
   </ItemGroup>
 
diff --git a/src/libraries/System.Net.Quic/tests/FunctionalTests/System.Net.Quic.Functional.Tests.csproj b/src/libraries/System.Net.Quic/tests/FunctionalTests/System.Net.Quic.Functional.Tests.csproj
index 62b1be2da62e95..fcd2679de2d437 100644
--- a/src/libraries/System.Net.Quic/tests/FunctionalTests/System.Net.Quic.Functional.Tests.csproj
+++ b/src/libraries/System.Net.Quic/tests/FunctionalTests/System.Net.Quic.Functional.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix</TargetFrameworks>
     <EnablePreviewFeatures>true</EnablePreviewFeatures>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj b/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
index d16970c9a19a91..051c2bc0df855c 100644
--- a/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
+++ b/src/libraries/System.Net.Requests/src/System.Net.Requests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
     <!-- SYSLIB0014: WebRequest, HttpWebRequest, ServicePoint, and WebClient are obsolete. Use HttpClient instead. -->
     <NoWarn>$(NoWarn);SYSLIB0014</NoWarn>
   </PropertyGroup>
@@ -86,7 +86,7 @@
              Link="Common\System\Net\ContextAwareResult.Windows.cs" />
     <Compile Include="System\Net\WebExceptionPal.Windows.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="$(CommonPath)System\Net\ContextAwareResult.Unix.cs"
              Link="Common\System\Net\ContextAwareResult.Unix.cs" />
     <Compile Include="System\Net\WebExceptionPal.Unix.cs" />
diff --git a/src/libraries/System.Net.Security/src/System.Net.Security.csproj b/src/libraries/System.Net.Security/src/System.Net.Security.csproj
index 3ff9a0bf97a192..af280c25779ed9 100644
--- a/src/libraries/System.Net.Security/src/System.Net.Security.csproj
+++ b/src/libraries/System.Net.Security/src/System.Net.Security.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)</TargetFrameworks>
     <!-- This is needed so that code for TlsCipherSuite will have no namespace (causes compile errors) when used within T4 template  -->
     <DefineConstants>$(DefineConstants);PRODUCT</DefineConstants>
     <EnableAOTAnalyzer>true</EnableAOTAnalyzer>
@@ -11,9 +11,9 @@
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.SystemNetSecurity_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
     <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'windows'">$(DefineConstants);TARGET_WINDOWS</DefineConstants>
-    <UseAndroidCrypto Condition="'$(TargetPlatformIdentifier)' == 'Android'">true</UseAndroidCrypto>
-    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</UseAppleCrypto>
-    <UseManagedNtlm Condition="'$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</UseManagedNtlm>
+    <UseAndroidCrypto Condition="'$(TargetPlatformIdentifier)' == 'android'">true</UseAndroidCrypto>
+    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</UseAppleCrypto>
+    <UseManagedNtlm Condition="'$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'tvos'">true</UseManagedNtlm>
     <DefineConstants Condition="'$(UseAndroidCrypto)' == 'true' or '$(UseAppleCrypto)' == 'true'">$(DefineConstants);SYSNETSECURITY_NO_OPENSSL</DefineConstants>
     <GenAPIExcludeApiList>ReferenceAssemblyExclusions.txt</GenAPIExcludeApiList>
   </PropertyGroup>
diff --git a/src/libraries/System.Net.Security/tests/EnterpriseTests/System.Net.Security.Enterprise.Tests.csproj b/src/libraries/System.Net.Security/tests/EnterpriseTests/System.Net.Security.Enterprise.Tests.csproj
index ae538e6fa70a02..809f2f3023b19d 100644
--- a/src/libraries/System.Net.Security/tests/EnterpriseTests/System.Net.Security.Enterprise.Tests.csproj
+++ b/src/libraries/System.Net.Security/tests/EnterpriseTests/System.Net.Security.Enterprise.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <!-- NegotiateStream Tests -->
diff --git a/src/libraries/System.Net.Security/tests/FunctionalTests/System.Net.Security.Tests.csproj b/src/libraries/System.Net.Security/tests/FunctionalTests/System.Net.Security.Tests.csproj
index 7c3d432f34cb46..76bef62ae716af 100644
--- a/src/libraries/System.Net.Security/tests/FunctionalTests/System.Net.Security.Tests.csproj
+++ b/src/libraries/System.Net.Security/tests/FunctionalTests/System.Net.Security.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
     <!-- the res/xml/network_security_config.xml file comes from the System.Net.TestData package -->
@@ -17,7 +17,7 @@
     <RdXmlFile Include="default.rd.xml" />
   </ItemGroup>
   <Import Project="$(CommonTestPath)System\Net\Security\Kerberos\System.Net.Security.Kerberos.Shared.projitems" />
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="SslStreamExtensions.cs" />
     <Compile Include="TestConfiguration.cs" />
     <Compile Include="TestHelper.cs" />
@@ -118,7 +118,7 @@
     <Compile Include="SslStreamCredentialCacheTest.cs" />
     <Compile Include="SslStreamSystemDefaultsTest.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="TelemetryTest.cs" />
     <Compile Include="LoggingTest.cs" />
     <Compile Include="$(CommonTestPath)System\Diagnostics\Tracing\TestEventListener.cs"
@@ -144,7 +144,7 @@
     <Compile Include="$(CommonPath)Interop\Windows\Crypt32\Interop.MsgEncodingType.cs"
              Link="Common\Interop\Windows\Crypt32\Interop.MsgEncodingType.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="IdentityValidator.Unix.cs" />
     <Compile Include="$(CommonTestPath)System\Net\Capability.Security.Unix.cs"
              Link="Common\System\Net\Capability.Security.Unix.cs" />
diff --git a/src/libraries/System.Net.Security/tests/UnitTests/System.Net.Security.Unit.Tests.csproj b/src/libraries/System.Net.Security/tests/UnitTests/System.Net.Security.Unit.Tests.csproj
index 1d7184003daa5f..512eded0334207 100644
--- a/src/libraries/System.Net.Security/tests/UnitTests/System.Net.Security.Unit.Tests.csproj
+++ b/src/libraries/System.Net.Security/tests/UnitTests/System.Net.Security.Unit.Tests.csproj
@@ -10,14 +10,14 @@
     <NoWarn>436</NoWarn>
     <!-- Disable: CLSCompliant attribute is not needed -->
     <NoWarn>$(NoWarn);3021</NoWarn>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-Android</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-android</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="AssemblyInfo.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="SslApplicationProtocolTests.cs" />
     <Compile Include="SslAuthenticationOptionsTests.cs" />
     <Compile Include="SslStreamAllowedProtocolsTest.cs" />
@@ -42,7 +42,7 @@
     <Compile Include="$(CommonPath)System\HexConverter.cs"
              Link="Common\System\HexConverter.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <!-- Production code references -->
     <Compile Include="$(CommonPath)System\Net\Security\MD4.cs"
              Link="Common\System\Net\Security\MD4.cs" />
@@ -95,7 +95,7 @@
   </ItemGroup>
 
   <!-- NT Authentication -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="$(CommonPath)System\Net\ContextFlagsPal.cs"
              Link="Common\System\Net\ContextFlagsPal.cs" />
     <Compile Include="$(CommonPath)System\Net\DebugSafeHandleZeroOrMinusOneIsInvalid.cs"
@@ -117,7 +117,7 @@
   </ItemGroup>
 
   <!-- Unix specific files (NT Authentication) -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Net.Security.Native\Interop.GssBuffer.cs"
diff --git a/src/libraries/System.Net.Sockets/src/System.Net.Sockets.csproj b/src/libraries/System.Net.Sockets/src/System.Net.Sockets.csproj
index e62cf75ea26417..e50db90c453e7c 100644
--- a/src/libraries/System.Net.Sockets/src/System.Net.Sockets.csproj
+++ b/src/libraries/System.Net.Sockets/src/System.Net.Sockets.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -182,7 +182,7 @@
     <Compile Include="$(CommonPath)System\Net\CompletionPortHelper.Windows.cs"
              Link="Common\System\Net\CompletionPortHelper.Windows.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Compile Include="System\Net\Sockets\SafeSocketHandle.Unix.cs" />
     <Compile Include="System\Net\Sockets\Socket.Unix.cs" />
     <Compile Include="System\Net\Sockets\SocketAsyncContext.Unix.cs" />
@@ -300,7 +300,7 @@
     <Reference Include="System.Threading.Overlapped" />
     <Reference Include="System.Threading.ThreadPool" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix'">
     <Reference Include="System.Threading.Thread" />
   </ItemGroup>
 </Project>
diff --git a/src/libraries/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj b/src/libraries/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj
index 884db1eea549e0..e1f59297946a32 100644
--- a/src/libraries/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj
+++ b/src/libraries/System.Net.Sockets/tests/FunctionalTests/System.Net.Sockets.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <IgnoreForCI Condition="'$(TargetOS)' == 'Browser'">true</IgnoreForCI>
     <EventSourceSupport Condition="'$(TestNativeAot)' == 'true'">true</EventSourceSupport>
   </PropertyGroup>
@@ -20,7 +20,7 @@
     <Compile Include="DnsEndPointTest.cs" />
     <Compile Include="DualModeSocketTest.cs" />
     <Compile Include="ExecutionContextFlowTest.cs" />
-    <Compile Include="InlineCompletions.Unix.cs" Condition="'$(TargetPlatformIdentifier)' == 'Unix'"/>
+    <Compile Include="InlineCompletions.Unix.cs" Condition="'$(TargetPlatformIdentifier)' == 'unix'"/>
     <Compile Include="IPPacketInformationTest.cs" />
     <Compile Include="KeepAliveTest.cs" />
     <Compile Include="LingerStateTest.cs" />
diff --git a/src/libraries/System.Net.WebClient/src/System.Net.WebClient.csproj b/src/libraries/System.Net.WebClient/src/System.Net.WebClient.csproj
index 1fb12930ce1854..5db860c9126fc5 100644
--- a/src/libraries/System.Net.WebClient/src/System.Net.WebClient.csproj
+++ b/src/libraries/System.Net.WebClient/src/System.Net.WebClient.csproj
@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == 'Browser'">SR.SystemNetWebClient_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
+    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == 'browser'">SR.SystemNetWebClient_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
   </PropertyGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
     <Compile Include="System\Net\WebClient.cs" />
     <Compile Include="$(CommonPath)System\IO\DelegatingStream.cs"
              Link="Common\System\IO\DelegatingStream.cs" />
diff --git a/src/libraries/System.Net.WebProxy/src/System.Net.WebProxy.csproj b/src/libraries/System.Net.WebProxy/src/System.Net.WebProxy.csproj
index fbe0e197d113c3..68485c90ea3556 100644
--- a/src/libraries/System.Net.WebProxy/src/System.Net.WebProxy.csproj
+++ b/src/libraries/System.Net.WebProxy/src/System.Net.WebProxy.csproj
@@ -1,13 +1,13 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System\Net\IWebProxyScript.cs" />
     <Compile Include="System\Net\WebProxy.cs" />
-    <Compile Condition="'$(TargetPlatformIdentifier)' == 'Browser'" Include="System\Net\WebProxy.Browser.cs" />
-    <Compile Condition="'$(TargetPlatformIdentifier)' != 'Browser'" Include="System\Net\WebProxy.NonBrowser.cs" />
+    <Compile Condition="'$(TargetPlatformIdentifier)' == 'browser'" Include="System\Net\WebProxy.Browser.cs" />
+    <Compile Condition="'$(TargetPlatformIdentifier)' != 'browser'" Include="System\Net\WebProxy.NonBrowser.cs" />
   </ItemGroup>
   <ItemGroup>
     <Reference Include="System.Memory" />
diff --git a/src/libraries/System.Net.WebSockets.Client/src/System.Net.WebSockets.Client.csproj b/src/libraries/System.Net.WebSockets.Client/src/System.Net.WebSockets.Client.csproj
index b7da9d3e90becb..6642f381985eb3 100644
--- a/src/libraries/System.Net.WebSockets.Client/src/System.Net.WebSockets.Client.csproj
+++ b/src/libraries/System.Net.WebSockets.Client/src/System.Net.WebSockets.Client.csproj
@@ -1,25 +1,25 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <DefineConstants>$(DefineConstants);TARGET_BROWSER</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>
     <Compile Include="System\Net\WebSockets\ClientWebSocket.cs" />
     <Compile Include="System\Net\WebSockets\ClientWebSocketDeflateConstants.cs" />
-    <Compile Include="System\Net\WebSockets\ClientWebSocketOptions.cs" Condition="'$(TargetPlatformIdentifier)' != 'Browser'" />
     <Compile Include="$(CommonPath)System\Net\UriScheme.cs" Link="Common\System\Net\UriScheme.cs" />
     <Compile Include="$(CommonPath)System\Net\WebSockets\WebSocketValidate.cs" Link="Common\System\Net\WebSockets\WebSocketValidate.cs" />
     <Compile Include="System\Net\WebSockets\HttpResponseHeadersReadOnlyCollection.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'browser'">
+    <Compile Include="System\Net\WebSockets\ClientWebSocketOptions.cs" />
     <Compile Include="System\Net\WebSockets\WebSocketHandle.Managed.cs" />
     <Compile Include="$(CommonPath)System\Net\HttpKnownHeaderNames.cs" Link="Common\System\Net\HttpKnownHeaderNames.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\Net\WebSockets\WebSocketHandle.Browser.cs" />
     <Compile Include="System\Net\WebSockets\BrowserWebSockets\BrowserInterop.cs" />
     <Compile Include="System\Net\WebSockets\BrowserWebSockets\BrowserWebSocket.cs" />
@@ -40,10 +40,10 @@
     <Reference Include="System.Threading" />
     <Reference Include="System.Net.Http" />
     <Reference Include="System.Security.Cryptography" />
-    <Reference Include="System.Threading.Channels" Condition="'$(TargetPlatformIdentifier)' == 'Browser'" />
+    <Reference Include="System.Threading.Channels" Condition="'$(TargetPlatformIdentifier)' == 'browser'" />
     <Reference Include="System.Memory" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <ProjectReference Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\gen\JSImportGenerator\JSImportGenerator.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
     <Reference Include="System.Runtime.InteropServices.JavaScript" />
   </ItemGroup>
diff --git a/src/libraries/System.Net.WebSockets.Client/tests/System.Net.WebSockets.Client.Tests.csproj b/src/libraries/System.Net.WebSockets.Client/tests/System.Net.WebSockets.Client.Tests.csproj
index f0ba87aa3c6c51..603607b9e49eb0 100644
--- a/src/libraries/System.Net.WebSockets.Client/tests/System.Net.WebSockets.Client.Tests.csproj
+++ b/src/libraries/System.Net.WebSockets.Client/tests/System.Net.WebSockets.Client.Tests.csproj
@@ -3,7 +3,7 @@
 
   <PropertyGroup>
     <StringResourcesPath>../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <DefineConstants>$(DefineConstants);NETSTANDARD</DefineConstants>
     <!--Remove once this is fixed, https://github.com/dotnet/runtime/issues/71506 -->
     <IlcTrimMetadata>false</IlcTrimMetadata>
diff --git a/src/libraries/System.Net.WebSockets.Client/tests/wasm/System.Net.WebSockets.Client.Wasm.Tests.csproj b/src/libraries/System.Net.WebSockets.Client/tests/wasm/System.Net.WebSockets.Client.Wasm.Tests.csproj
index 0a27428b1d7fb5..b01e12688a4eb6 100644
--- a/src/libraries/System.Net.WebSockets.Client/tests/wasm/System.Net.WebSockets.Client.Wasm.Tests.csproj
+++ b/src/libraries/System.Net.WebSockets.Client/tests/wasm/System.Net.WebSockets.Client.Wasm.Tests.csproj
@@ -3,7 +3,7 @@
 
   <PropertyGroup>
     <StringResourcesPath>../../src/Resources/Strings.resx</StringResourcesPath>
-    <TargetFramework>$(NetCoreAppCurrent)-Browser</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-browser</TargetFramework>
     <DefineConstants>$(DefineConstants);NETSTANDARD</DefineConstants>
   </PropertyGroup>
 
diff --git a/src/libraries/System.Net.WebSockets/src/System.Net.WebSockets.csproj b/src/libraries/System.Net.WebSockets/src/System.Net.WebSockets.csproj
index c0c4ded0d332a0..f9ef1c7848c47c 100644
--- a/src/libraries/System.Net.WebSockets/src/System.Net.WebSockets.csproj
+++ b/src/libraries/System.Net.WebSockets/src/System.Net.WebSockets.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
@@ -40,7 +40,7 @@
              Link="Common\Interop\Windows\Interop.Libraries.cs" />
   </ItemGroup>
   <!-- Unix specific files -->
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser' ">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser' ">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs"
              Link="Common\Interop\Unix\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Resources.Extensions/tests/System.Resources.Extensions.Tests.csproj b/src/libraries/System.Resources.Extensions/tests/System.Resources.Extensions.Tests.csproj
index f8a1aed6152a18..2c2920807ecdad 100644
--- a/src/libraries/System.Resources.Extensions/tests/System.Resources.Extensions.Tests.csproj
+++ b/src/libraries/System.Resources.Extensions/tests/System.Resources.Extensions.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetFrameworkMinimum)</TargetFrameworks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Resources.ResourceManager/tests/System.Resources.ResourceManager.Tests.csproj b/src/libraries/System.Resources.ResourceManager/tests/System.Resources.ResourceManager.Tests.csproj
index 66cb937a3d1e20..ecd51dc88d663b 100644
--- a/src/libraries/System.Resources.ResourceManager/tests/System.Resources.ResourceManager.Tests.csproj
+++ b/src/libraries/System.Resources.ResourceManager/tests/System.Resources.ResourceManager.Tests.csproj
@@ -4,7 +4,7 @@
     <BinPlaceSatelliteAssemblies>true</BinPlaceSatelliteAssemblies>
     <TestRuntime>true</TestRuntime>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="MissingManifestResourceExceptionTests.cs" />
diff --git a/src/libraries/System.Runtime.Extensions/tests/System.Runtime.Extensions.Tests.csproj b/src/libraries/System.Runtime.Extensions/tests/System.Runtime.Extensions.Tests.csproj
index a9a3ad28024042..3e2285f9612c32 100644
--- a/src/libraries/System.Runtime.Extensions/tests/System.Runtime.Extensions.Tests.csproj
+++ b/src/libraries/System.Runtime.Extensions/tests/System.Runtime.Extensions.Tests.csproj
@@ -4,12 +4,12 @@
     <TestRuntime>true</TestRuntime>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <EnableLibraryImportGenerator>true</EnableLibraryImportGenerator>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">$(DefineConstants);Unix</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">$(DefineConstants);Unix</DefineConstants>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System\ApplicationIdTests.cs" />
@@ -81,7 +81,7 @@
     <Compile Include="System\Runtime\ProfileOptimization.cs" />
     <Compile Include="System\Runtime\CompilerServices\SwitchExpressionExceptionTests.cs" />
 
-    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetHostName.cs" Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'" Link="Common\Interop\Unix\System.Native\Interop.GetHostName.cs" />
+    <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetHostName.cs" Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'" Link="Common\Interop\Unix\System.Native\Interop.GetHostName.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Common\Interop\Unix\Interop.Libraries.cs" />
     <Compile Include="$(CommonTestPath)System\Diagnostics\DebuggerAttributes.cs" Link="Common\System\Diagnostics\DebuggerAttributes.cs" />
     <Compile Include="$(CommonTestPath)System\IO\PathFeatures.cs" Link="Common\System\IO\PathFeatures.cs" />
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
index f67b0cd3b0346d..d80caca82ba841 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <FeatureWasmThreads Condition="'$(TargetOS)' == 'Browser' and ('$(WasmEnableThreads)' == 'true' or '$(MonoWasmBuildVariant)' == 'multithread')">true</FeatureWasmThreads>
     <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'" >$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
@@ -9,14 +9,14 @@
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' != 'Browser'">SR.SystemRuntimeInteropServicesJavaScript_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
+    <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' != 'browser'">SR.SystemRuntimeInteropServicesJavaScript_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
   </PropertyGroup>
 
   <ItemGroup>
     <Compile Include="System.Runtime.InteropServices.JavaScript.SupportedOSPlatform.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="$(CommonPath)Interop\Browser\Interop.Runtime.cs" Link="System\Runtime\InteropServices\JavaScript\Interop\Interop.Runtime.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\JavaScriptImports.Generated.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\JavaScriptExports.cs" />
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj
index e7643c86db59b3..b310c819c66749 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFramework>$(NetCoreAppCurrent)-Browser</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-browser</TargetFramework>
     <TestRuntime>true</TestRuntime>
     <WasmXHarnessArgs>$(WasmXHarnessArgs) --engine-arg=--expose-gc --web-server-use-cop</WasmXHarnessArgs>
     <NoWarn>0612</NoWarn>
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj
index e6e1d2adcf81ec..2db86ee5eb768e 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <TestRuntime>true</TestRuntime>
     <WasmXHarnessArgs>$(WasmXHarnessArgs) --engine-arg=--expose-gc --web-server-use-cop</WasmXHarnessArgs>
     <!-- Use following lines to write the generated files to disk. -->
diff --git a/src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/System.Runtime.InteropServices.RuntimeInformation.Tests.csproj b/src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/System.Runtime.InteropServices.RuntimeInformation.Tests.csproj
index 3edd7d47f72ab3..9b5b6f3aedd552 100644
--- a/src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/System.Runtime.InteropServices.RuntimeInformation.Tests.csproj
+++ b/src/libraries/System.Runtime.InteropServices.RuntimeInformation/tests/System.Runtime.InteropServices.RuntimeInformation.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="CheckArchitectureTests.cs" />
diff --git a/src/libraries/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.UnitTests/System.Runtime.InteropServices.Tests.csproj b/src/libraries/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.UnitTests/System.Runtime.InteropServices.Tests.csproj
index 867c373eea2a9e..90173a66a48c68 100644
--- a/src/libraries/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.UnitTests/System.Runtime.InteropServices.Tests.csproj
+++ b/src/libraries/System.Runtime.InteropServices/tests/System.Runtime.InteropServices.UnitTests/System.Runtime.InteropServices.Tests.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <TestRuntime>true</TestRuntime>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
   </PropertyGroup>
@@ -189,7 +189,7 @@
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'windows'">
     <Compile Include="System\Runtime\InteropServices\PosixSignalRegistrationTests.Windows.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\Runtime\InteropServices\PosixSignalRegistrationTests.Unix.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Libraries.cs" Link="Common\Interop\Unix\Interop.Libraries.cs" />
   </ItemGroup>
diff --git a/src/libraries/System.Runtime.Intrinsics/tests/System.Runtime.Intrinsics.Tests.csproj b/src/libraries/System.Runtime.Intrinsics/tests/System.Runtime.Intrinsics.Tests.csproj
index 3009539cc05335..faec945cf5fef3 100644
--- a/src/libraries/System.Runtime.Intrinsics/tests/System.Runtime.Intrinsics.Tests.csproj
+++ b/src/libraries/System.Runtime.Intrinsics/tests/System.Runtime.Intrinsics.Tests.csproj
@@ -4,7 +4,7 @@
     <NoWarn>$(NoWarn),1718,SYSLIB0013</NoWarn>
     <TestRuntime>true</TestRuntime>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <!-- Disable nullability public only feature for NullabilityInfoContextTests -->
     <Features>$(Features.Replace('nullablePublicOnly', '')</Features>
   </PropertyGroup>
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj b/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
index bbb10a1f4ce4b7..6e1e9d6c98151e 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
+++ b/src/libraries/System.Runtime.Serialization.Formatters/src/System.Runtime.Serialization.Formatters.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Android</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-android</TargetFrameworks>
     <!-- ILLinker settings -->
     <ILLinkDirectory>$(MSBuildThisFileDirectory)ILLink\</ILLinkDirectory>
     <EnableAOTAnalyzer>true</EnableAOTAnalyzer>
diff --git a/src/libraries/System.Runtime.Serialization.Formatters/tests/System.Runtime.Serialization.Formatters.Tests.csproj b/src/libraries/System.Runtime.Serialization.Formatters/tests/System.Runtime.Serialization.Formatters.Tests.csproj
index 378b38abb9353a..9aca7a64fff959 100644
--- a/src/libraries/System.Runtime.Serialization.Formatters/tests/System.Runtime.Serialization.Formatters.Tests.csproj
+++ b/src/libraries/System.Runtime.Serialization.Formatters/tests/System.Runtime.Serialization.Formatters.Tests.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <TestRuntime>true</TestRuntime>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-FreeBSD;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-Solaris;$(NetCoreAppCurrent)-Linux;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;net48</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-freebsd;$(NetCoreAppCurrent)-illumos;$(NetCoreAppCurrent)-solaris;$(NetCoreAppCurrent)-linux;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;net48</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="BinaryFormatterTestData.cs" />
diff --git a/src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj b/src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj
index 54d3aaacd76050..6135fc76923dee 100644
--- a/src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj
+++ b/src/libraries/System.Runtime/tests/System.Runtime.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <NoWarn>$(NoWarn),1718,SYSLIB0013</NoWarn>
     <TestRuntime>true</TestRuntime>
@@ -260,7 +260,7 @@
     <Compile Include="$(CommonTestPath)System\RandomDataGenerator.cs" Link="Common\System\RandomDataGenerator.cs" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'browser'">
     <Compile Include="System\ExitCodeTests.Unix.cs" />
   </ItemGroup>
 
diff --git a/src/libraries/System.Security.Cryptography.Csp/tests/System.Security.Cryptography.Csp.Tests.csproj b/src/libraries/System.Security.Cryptography.Csp/tests/System.Security.Cryptography.Csp.Tests.csproj
index 59d139c7749920..54aeb5640192e0 100644
--- a/src/libraries/System.Security.Cryptography.Csp/tests/System.Security.Cryptography.Csp.Tests.csproj
+++ b/src/libraries/System.Security.Cryptography.Csp/tests/System.Security.Cryptography.Csp.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <!-- SYSLIB0021: Derived cryptographic types are obsolete -->
     <NoWarn>$(NoWarn);SYSLIB0021</NoWarn>
     <!--Remove once this is fixed, https://github.com/dotnet/runtime/issues/71506 -->
diff --git a/src/libraries/System.Security.Cryptography.OpenSsl/tests/System.Security.Cryptography.OpenSsl.Tests.csproj b/src/libraries/System.Security.Cryptography.OpenSsl/tests/System.Security.Cryptography.OpenSsl.Tests.csproj
index 5e70c34c074dfb..37bd485fcf20b0 100644
--- a/src/libraries/System.Security.Cryptography.OpenSsl/tests/System.Security.Cryptography.OpenSsl.Tests.csproj
+++ b/src/libraries/System.Security.Cryptography.OpenSsl/tests/System.Security.Cryptography.OpenSsl.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <!-- The library is not supported on mobile platforms (PNSE) -->
     <IgnoreForCI Condition="'$(TargetOS)' == 'Android' or '$(TargetOS)' == 'iOS' or '$(TargetOS)' == 'tvOS'">true</IgnoreForCI>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
diff --git a/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj b/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
index 99e10abbe05951..aa1ef1c756831a 100644
--- a/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
+++ b/src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj
@@ -2,7 +2,7 @@
   <PropertyGroup>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <DefineConstants>$(DefineConstants);INTERNAL_ASYMMETRIC_IMPLEMENTATIONS</DefineConstants>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
     <NoWarn>$(NoWarn);CA5350;CA5351;CA5379;CA5384;SYSLIB0026</NoWarn>
     <!-- PasswordDeriveBytes.GetBytes is obsolete but DeriveBytes.GetBytes intentionally isn't. -->
     <NoWarn>$(NoWarn);CS0809</NoWarn>
@@ -12,10 +12,10 @@
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' == ''">SR.SystemSecurityCryptography_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
-    <UseAndroidCrypto Condition="'$(TargetPlatformIdentifier)' == 'Android'">true</UseAndroidCrypto>
-    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</UseAppleCrypto>
-    <UseOpenSsl Condition="'$(TargetPlatformIdentifier)' == 'Unix'">true</UseOpenSsl>
-    <UseOpenSslAead Condition="'$(UseOpenSsl)' == 'true' or '$(TargetPlatformIdentifier)' == 'OSX'">true</UseOpenSslAead>
+    <UseAndroidCrypto Condition="'$(TargetPlatformIdentifier)' == 'android'">true</UseAndroidCrypto>
+    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</UseAppleCrypto>
+    <UseOpenSsl Condition="'$(TargetPlatformIdentifier)' == 'unix'">true</UseOpenSsl>
+    <UseOpenSslAead Condition="'$(UseOpenSsl)' == 'true' or '$(TargetPlatformIdentifier)' == 'osx'">true</UseOpenSslAead>
     <NeedOpenSslInitializer Condition="'$(UseOpenSslAead)' == 'true'">true</NeedOpenSslInitializer>
   </PropertyGroup>
 
@@ -549,7 +549,7 @@
       <DependentUpon>System\Security\Cryptography\X509Certificates\Asn1\PolicyInformationAsn.xml</DependentUpon>
     </Compile>
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser'">
     <!-- GetRandomBytes is identical on Unix and Browser -->
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetRandomBytes.cs"
              Link="Common\Interop\Unix\System.Native\Interop.GetRandomBytes.cs" />
@@ -1219,7 +1219,7 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\X509Pal.Apple.ECKey.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X509Pal.Apple.X500Name.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\Asn1SafeHandles.Unix.cs"
              Link="Common\Microsoft\Win32\SafeHandles\Asn1SafeHandles.Unix.cs" />
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeBignumHandle.Unix.cs"
@@ -1312,7 +1312,7 @@
     <Compile Include="System\Security\Cryptography\X509Certificates\StorePal.macOS.LoaderPal.cs" />
     <Compile Include="System\Security\Cryptography\X509Certificates\X509Pal.macOS.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' != 'OSX'">
+  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' != 'osx'">
     <Compile Include="$(CommonPath)Interop\OSX\System.Security.Cryptography.Native.Apple\Interop.Keychain.iOS.cs"
              Link="Common\Interop\OSX\System.Security.Cryptography.Native.Apple\Interop.Keychain.iOS.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\System.Security.Cryptography.Native.Apple\Interop.X509.iOS.cs"
@@ -1836,7 +1836,7 @@
     <Reference Include="System.Threading" />
     <Reference Include="System.Threading.Thread" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier' != 'Browser'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != '' and '$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier' != 'browser'">
     <Reference Include="System.Console" Condition="'$(Configuration)' == 'Debug'" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/libraries/System.Security.Cryptography/tests/System.Security.Cryptography.Tests.csproj b/src/libraries/System.Security.Cryptography/tests/System.Security.Cryptography.Tests.csproj
index 182dcbddd426ab..a24845e6891c85 100644
--- a/src/libraries/System.Security.Cryptography/tests/System.Security.Cryptography.Tests.csproj
+++ b/src/libraries/System.Security.Cryptography/tests/System.Security.Cryptography.Tests.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-Unix;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-OSX;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-windows;$(NetCoreAppCurrent)-unix;$(NetCoreAppCurrent)-android;$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)-osx;$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
     <NoWarn>$(NoWarn);SYSLIB0021;SYSLIB0026;SYSLIB0027;SYSLIB0028</NoWarn>
@@ -13,10 +13,10 @@
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Unix' or '$(TargetPlatformIdentifier)' == 'Android' or '$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">$(DefineConstants);Unix</DefineConstants>
-    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'OSX' or '$(TargetPlatformIdentifier)' == 'iOS' or '$(TargetPlatformIdentifier)' == 'tvOS'">true</UseAppleCrypto>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'unix' or '$(TargetPlatformIdentifier)' == 'android' or '$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">$(DefineConstants);Unix</DefineConstants>
+    <UseAppleCrypto Condition="'$(TargetPlatformIdentifier)' == 'osx' or '$(TargetPlatformIdentifier)' == 'ios' or '$(TargetPlatformIdentifier)' == 'tvos'">true</UseAppleCrypto>
   </PropertyGroup>
-  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == 'Android'">
+  <PropertyGroup Condition="'$(TargetPlatformIdentifier)' == 'android'">
     <UseAndroidCrypto>true</UseAndroidCrypto>
     <XUnitSingleThreadedMode>true</XUnitSingleThreadedMode>
     <XUnitUseRandomizedTestOrderer>true</XUnitUseRandomizedTestOrderer>
@@ -388,10 +388,10 @@
   <ItemGroup Condition="'$(UseAndroidCrypto)' != 'true'">
     <Compile Include="X509Certificates\RevocationTests\DynamicRevocationTests.Default.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' != 'OSX'">
+  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' != 'osx'">
     <Compile Include="X509Certificates\X509StoreMutableTests.iOS.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' == 'OSX'">
+  <ItemGroup Condition="'$(UseAppleCrypto)' == 'true' and '$(TargetPlatformIdentifier)' == 'osx'">
     <Compile Include="X509Certificates\X509StoreMutableTests.OSX.cs" />
     <Compile Include="$(CommonPath)Interop\OSX\Interop.CoreFoundation.cs"
              Link="Common\Interop\OSX\Interop.CoreFoundation.cs" />
@@ -420,7 +420,7 @@
     <Compile Include="$(CommonPath)Microsoft\Win32\SafeHandles\SafeHandleCache.cs"
              Link="Common\Microsoft\Win32\SafeHandles\SafeHandleCache.cs" />
   </ItemGroup>
-  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'Browser' and '$(UseAndroidCrypto)' != 'true' and '$(UseAppleCrypto)' != 'true'">
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' != 'windows' and '$(TargetPlatformIdentifier)' != 'browser' and '$(UseAndroidCrypto)' != 'true' and '$(UseAppleCrypto)' != 'true'">
     <Compile Include="$(CommonPath)Interop\Unix\Interop.Errors.cs"
              Link="Common\Interop\Unix\Interop.Errors.cs" />
     <Compile Include="$(CommonPath)Interop\Unix\System.Native\Interop.GetEUid.cs"
diff --git a/src/libraries/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj b/src/libraries/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
index a0e2f162efeb4c..8baa4cc0619974 100644
--- a/src/libraries/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
+++ b/src/libraries/System.Text.Encodings.Web/src/System.Text.Encodings.Web.csproj
@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-Browser;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-Browser;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent);$(NetCoreAppPrevious)-browser;$(NetCoreAppPrevious);$(NetCoreAppMinimum)-browser;$(NetCoreAppMinimum);netstandard2.0;$(NetFrameworkMinimum)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <!-- CS3011: Only CLS-compliant members can be abstract -->
     <!-- CS3019: CLS attributes on internal types. Some shared source files are internal in this project. -->
@@ -17,7 +17,7 @@ System.Text.Encodings.Web.JavaScriptEncoder</PackageDescription>
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
-    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'Browser'">$(DefineConstants);TARGET_BROWSER</DefineConstants>
+    <DefineConstants Condition="'$(TargetPlatformIdentifier)' == 'browser'">$(DefineConstants);TARGET_BROWSER</DefineConstants>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/src/libraries/apicompat/ApiCompat.proj b/src/libraries/apicompat/ApiCompat.proj
index 0a36ff6d36a45d..210f60e5f85156 100644
--- a/src/libraries/apicompat/ApiCompat.proj
+++ b/src/libraries/apicompat/ApiCompat.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.NoTargets">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <!-- Reference the dependencies to have the assemblies available for API comparison. -->
     <NoTargetsDoNotReferenceOutputAssemblies>false</NoTargetsDoNotReferenceOutputAssemblies>
     <!-- Target reference assemblies instead of implementation assemblies. -->
diff --git a/src/libraries/oob-src.proj b/src/libraries/oob-src.proj
index 472a2dfb5e7082..60c713c88940cf 100644
--- a/src/libraries/oob-src.proj
+++ b/src/libraries/oob-src.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.Traversal">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <!-- Filter ProjectReferences to build the best matching target framework only. -->
     <FilterTraversalProjectReferences>true</FilterTraversalProjectReferences>
   </PropertyGroup>
@@ -18,7 +18,7 @@
     <!-- During an official Build, build the rid specific package matching the OutputRid only outside of an allconfigurations build and only when targeting the CoreCLR runtime.
          The limitation on the CoreCLR runtime is entirely artificial but avoids duplicate assets being publish. -->
     <ProjectReference Include="$(MSBuildThisFileDirectory)*\pkg\runtime.$(OutputRid).*.proj" Condition="'$(BuildingAnOfficialBuildLeg)' != 'true' or
-                                                                                                            ('$(BuildAllConfigurations)' != 'true' and '$(RuntimeFlavor)' == '$(PrimaryRuntimeFlavor)')" />
+                                                                                                        ('$(BuildAllConfigurations)' != 'true' and '$(RuntimeFlavor)' == '$(PrimaryRuntimeFlavor)')" />
 
     <!-- Don't build task and tools project in the NetCoreAppCurrent vertical. -->
     <ProjectReference Remove="Microsoft.XmlSerializer.Generator\src\Microsoft.XmlSerializer.Generator.csproj" />
diff --git a/src/libraries/oob.proj b/src/libraries/oob.proj
index 747597169ba135..792670cb803ba1 100644
--- a/src/libraries/oob.proj
+++ b/src/libraries/oob.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.NoTargets">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <!-- By default, build the NetCoreAppCurrent vertical only. -->
     <BuildTargetFramework Condition="'$(BuildAllConfigurations)' != 'true'">$(NetCoreAppCurrent)</BuildTargetFramework>
   </PropertyGroup>
diff --git a/src/libraries/sfx-src.proj b/src/libraries/sfx-src.proj
index 8e7679dac15eb8..8550791478ff5d 100644
--- a/src/libraries/sfx-src.proj
+++ b/src/libraries/sfx-src.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.Traversal">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <!-- Filter ProjectReferences to build the best matching target framework only. -->
     <FilterTraversalProjectReferences>true</FilterTraversalProjectReferences>
   </PropertyGroup>
diff --git a/src/libraries/sfx.proj b/src/libraries/sfx.proj
index e57141d588b707..e5a4e31c7dd0c6 100644
--- a/src/libraries/sfx.proj
+++ b/src/libraries/sfx.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.NoTargets">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <BuildInParallel>false</BuildInParallel>
   </PropertyGroup>
 
diff --git a/src/libraries/shims.proj b/src/libraries/shims.proj
index 5c138fd1e7063c..c0a1415b6443eb 100644
--- a/src/libraries/shims.proj
+++ b/src/libraries/shims.proj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.Build.Traversal">
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
   </PropertyGroup>
 
   <!-- Reference the source project shims which themselves then reference their corresponding ref project, if it exists. -->
diff --git a/src/libraries/shims/Directory.Build.props b/src/libraries/shims/Directory.Build.props
index aa98afd27a62a0..52d31dadd2f2fe 100644
--- a/src/libraries/shims/Directory.Build.props
+++ b/src/libraries/shims/Directory.Build.props
@@ -3,7 +3,7 @@
   <Import Project="..\Directory.Build.props" />
 
   <PropertyGroup>
-    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS)</TargetFramework>
+    <TargetFramework>$(NetCoreAppCurrent)-$(TargetOS.ToLowerInvariant())</TargetFramework>
     <Nullable>disable</Nullable>
     <!-- By default make shims compile against reference assemblies. -->
     <CompileUsingReferenceAssemblies>true</CompileUsingReferenceAssemblies>