diff --git a/dwds/debug_extension_mv3/web/chrome_api.dart b/dwds/debug_extension_mv3/web/chrome_api.dart
index 803e13082..77fc960f8 100644
--- a/dwds/debug_extension_mv3/web/chrome_api.dart
+++ b/dwds/debug_extension_mv3/web/chrome_api.dart
@@ -170,6 +170,8 @@ class Runtime {
 
   external Object getManifest();
 
+  external String getURL(String path);
+
   // Note: Not checking the lastError when one occurs throws a runtime exception.
   external ChromeError? get lastError;
 
diff --git a/dwds/debug_extension_mv3/web/debug_info.dart b/dwds/debug_extension_mv3/web/debug_info.dart
new file mode 100644
index 000000000..b827a4160
--- /dev/null
+++ b/dwds/debug_extension_mv3/web/debug_info.dart
@@ -0,0 +1,33 @@
+// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@JS()
+library debug_info;
+
+import 'dart:convert';
+import 'dart:html';
+import 'dart:js';
+
+import 'package:dwds/data/debug_info.dart';
+import 'package:dwds/data/serializers.dart';
+import 'package:js/js.dart';
+
+void main() {
+  final debugInfoJson = _readDartDebugInfo();
+  document.dispatchEvent(CustomEvent('dart-app-ready', detail: debugInfoJson));
+}
+
+String _readDartDebugInfo() {
+  final windowContext = JsObject.fromBrowserObject(window);
+
+  return jsonEncode(serializers.serialize(DebugInfo((b) => b
+    ..appEntrypointPath = windowContext['\$dartEntrypointPath']
+    ..appId = windowContext['\$dartAppId']
+    ..appInstanceId = windowContext['\$dartAppInstanceId']
+    ..appOrigin = window.location.origin
+    ..appUrl = window.location.href
+    ..extensionUrl = windowContext['\$dartExtensionUri']
+    ..isInternalBuild = windowContext['\$isInternalBuild']
+    ..isFlutterApp = windowContext['\$isFlutterApp'])));
+}
diff --git a/dwds/debug_extension_mv3/web/detector.dart b/dwds/debug_extension_mv3/web/detector.dart
index 0b9357844..76899834a 100644
--- a/dwds/debug_extension_mv3/web/detector.dart
+++ b/dwds/debug_extension_mv3/web/detector.dart
@@ -9,6 +9,7 @@ import 'dart:html';
 import 'dart:js_util';
 import 'package:js/js.dart';
 
+import 'chrome_api.dart';
 import 'logger.dart';
 import 'messaging.dart';
 
@@ -23,13 +24,26 @@ void _registerListeners() {
 void _onDartAppReadyEvent(Event event) {
   final debugInfo = getProperty(event, 'detail') as String?;
   if (debugInfo == null) {
-    debugError('Can\'t debug Dart app without debug info.', verbose: true);
-    return;
+    debugWarn(
+        'No debug info sent with ready event, instead reading from Window.');
+    _injectDebugInfoScript();
+  } else {
+    _sendMessageToBackgroundScript(
+      type: MessageType.debugInfo,
+      body: debugInfo,
+    );
   }
-  _sendMessageToBackgroundScript(
-    type: MessageType.debugInfo,
-    body: debugInfo,
-  );
+}
+
+// TODO(elliette): Remove once DWDS 17.0.0 is in Flutter stable. If we are on an
+// older version of DWDS, then the debug info is not sent along with the ready
+// event. Therefore we must read it from the Window object, which is slower.
+void _injectDebugInfoScript() {
+  final script = document.createElement('script');
+  final scriptSrc = chrome.runtime.getURL('debug_info.dart.js');
+  script.setAttribute('src', scriptSrc);
+  script.setAttribute('defer', true);
+  document.head?.append(script);
 }
 
 void _sendMessageToBackgroundScript({
diff --git a/dwds/debug_extension_mv3/web/manifest.json b/dwds/debug_extension_mv3/web/manifest.json
index 91efe797a..28c727f81 100644
--- a/dwds/debug_extension_mv3/web/manifest.json
+++ b/dwds/debug_extension_mv3/web/manifest.json
@@ -28,5 +28,11 @@
       "run_at": "document_end"
     }
   ],
+  "web_accessible_resources": [
+    {
+      "matches": ["<all_urls>"],
+      "resources": ["debug_info.dart.js"]
+    }
+  ],
   "options_page": "static_assets/settings.html"
 }
diff --git a/dwds/test/fixtures/utilities.dart b/dwds/test/fixtures/utilities.dart
index dacb24412..1f153da02 100644
--- a/dwds/test/fixtures/utilities.dart
+++ b/dwds/test/fixtures/utilities.dart
@@ -125,3 +125,31 @@ Future<T> retryFn<T>(
     failureMessage: failureMessage,
   );
 }
+
+/// Retries an asynchronous callback function with a delay until the result is
+/// non-null.
+Future<T> retryFnAsync<T>(
+  Future<T> Function() callback, {
+  int retryCount = 3,
+  int delayInMs = 1000,
+  String failureMessage = 'Function did not succeed after retries.',
+}) async {
+  if (retryCount == 0) {
+    throw Exception(failureMessage);
+  }
+
+  await Future.delayed(Duration(milliseconds: delayInMs));
+  try {
+    final result = await callback();
+    if (result != null) return result;
+  } catch (_) {
+    // Ignore any exceptions.
+  }
+
+  return retryFnAsync<T>(
+    callback,
+    retryCount: retryCount - 1,
+    delayInMs: delayInMs,
+    failureMessage: failureMessage,
+  );
+}
diff --git a/dwds/test/puppeteer/extension_test.dart b/dwds/test/puppeteer/extension_test.dart
index 065e50ceb..917c7e37e 100644
--- a/dwds/test/puppeteer/extension_test.dart
+++ b/dwds/test/puppeteer/extension_test.dart
@@ -22,6 +22,7 @@ import 'package:test/test.dart';
 import '../../debug_extension_mv3/web/data_serializers.dart';
 import '../../debug_extension_mv3/web/data_types.dart';
 import '../fixtures/context.dart';
+import '../fixtures/utilities.dart';
 import 'test_utils.dart';
 
 final context = TestContext.withSoundNullSafety();
@@ -435,6 +436,74 @@ void main() async {
         });
       }
     });
+
+    group('connected to a fake app', () {
+      final fakeAppPath = webCompatiblePath(
+        p.split(
+          absolutePath(
+            pathFromDwds: p.join(
+              'test',
+              'puppeteer',
+              'fake_app',
+              'index.html',
+            ),
+          ),
+        ),
+      );
+      final fakeAppUrl = 'file://$fakeAppPath';
+      late Browser browser;
+      late Worker worker;
+
+      setUpAll(() async {
+        browser = await puppeteer.launch(
+          headless: false,
+          timeout: Duration(seconds: 60),
+          args: [
+            '--load-extension=$extensionPath',
+            '--disable-extensions-except=$extensionPath',
+            '--disable-features=DialMediaRouteProvider',
+          ],
+        );
+        worker = await getServiceWorker(browser);
+        // Navigate to the Chrome extension page instead of the blank tab
+        // opened by Chrome. This is helpful for local debugging.
+        final blankTab = await navigateToPage(browser, url: 'about:blank');
+        await blankTab.goto('chrome://extensions/');
+      });
+
+      tearDown(() async {
+        await workerEvalDelay();
+        await worker.evaluate(_clearStorageJs());
+        await workerEvalDelay();
+      });
+
+      tearDownAll(() async {
+        await browser.close();
+      });
+
+      // Note: This tests that the debug extension still works for DWDS versions
+      // <17.0.0. Those versions don't send the debug info with the ready event.
+      // Therefore the values are read from the Window object.
+      test('reads debug info from Window and saves to storage', () async {
+        // Navigate to the "Dart" app:
+        await navigateToPage(browser, url: fakeAppUrl, isNew: true);
+        // Verify that we have debug info for the fake "Dart" app:
+        final appTabId = await _getTabId(fakeAppUrl, worker: worker);
+        final debugInfoKey = '$appTabId-debugInfo';
+        final debugInfo = await _fetchStorageObj<DebugInfo>(
+          debugInfoKey,
+          storageArea: 'session',
+          worker: worker,
+        );
+        expect(debugInfo.appId, equals('DART_APP_ID'));
+        expect(debugInfo.appEntrypointPath, equals('DART_ENTRYPOINT_PATH'));
+        expect(debugInfo.appInstanceId, equals('DART_APP_INSTANCE_ID'));
+        expect(debugInfo.isInternalBuild, isTrue);
+        expect(debugInfo.isFlutterApp, isFalse);
+        expect(debugInfo.appOrigin, isNotNull);
+        expect(debugInfo.appUrl, isNotNull);
+      });
+    });
   });
 }
 
@@ -521,11 +590,13 @@ Future<T> _fetchStorageObj<T>(
   required String storageArea,
   required Worker worker,
 }) async {
-  final storageObj = await worker.evaluate(_fetchStorageObjJs(
-    storageKey,
-    storageArea: storageArea,
-  ));
-  final json = storageObj[storageKey];
+  final json = await retryFnAsync<String>(() async {
+    final storageObj = await worker.evaluate(_fetchStorageObjJs(
+      storageKey,
+      storageArea: storageArea,
+    ));
+    return storageObj[storageKey];
+  });
   return serializers.deserialize(jsonDecode(json)) as T;
 }
 
diff --git a/dwds/test/puppeteer/fake_app/index.html b/dwds/test/puppeteer/fake_app/index.html
new file mode 100644
index 000000000..00e64ae27
--- /dev/null
+++ b/dwds/test/puppeteer/fake_app/index.html
@@ -0,0 +1,9 @@
+<html>
+  <head>
+    <script defer src="main.js"></script>
+  </head>
+
+  <body>
+    <h1>Fake app</h1>
+  </body>
+</html>
diff --git a/dwds/test/puppeteer/fake_app/main.js b/dwds/test/puppeteer/fake_app/main.js
new file mode 100644
index 000000000..04548baa5
--- /dev/null
+++ b/dwds/test/puppeteer/fake_app/main.js
@@ -0,0 +1,11 @@
+document.addEventListener("DOMContentLoaded", function(event) { 
+    window['$dartEntrypointPath'] = 'DART_ENTRYPOINT_PATH';
+    window['$dartAppId'] = 'DART_APP_ID';
+    window['$dartAppInstanceId'] = 'DART_APP_INSTANCE_ID';
+    window['$dartExtensionUri'] = 'DART_EXTENSION_URI';
+    window['$isInternalBuild'] = true;
+    window['$isFlutterApp'] = false;
+    setTimeout(() => {
+        window.top.document.dispatchEvent(new CustomEvent('dart-app-ready'));
+    }, 1000);
+  });