fix: Handle case-insensitive `www.` prefix #3769

vaskkey · 2025-09-26T12:42:47Z

Marked version:

16.3.0

Markdown flavor: Markdown.pl|CommonMark|GitHub Flavored Markdown|n/a

Description

Expectation

When a link starts with www. (in any case combination like Www., WWW., etc.), it should be automatically converted to a clickable link with http:// prepended.

Result

Before the fix, only lowercase www. was being prepended with http://. Links starting with Www. or other case variations were being processed as autolinks but did not have http:// prepended, which caused the links to redirect to http://mainwebsite/Www.foo.com.

After the fix, both www.foo.com and Www.foo.com are now properly converted to <a href="http://www.foo.com">www.foo.com</a> and <a href="http://Www.foo.com">Www.foo.com</a> respectively.

What was attempted

The fix was implemented in src/Tokenizer.ts:843 by changing the strict equality check from:

if (cap[1] === 'www.') {

to a case-insensitive comparison:

if (cap[1]?.toLowerCase() === 'www.') {

Contributor

Test(s) exist to ensure functionality and minimize regression (if no tests added, list tests covering this PR): Added cases to autolinks.md

Committer

In most cases, this should be a different person than the contributor.

CI is green (no forced merge required).
Squash and Merge PR following conventional commit guidelines.

vercel · 2025-09-26T12:42:53Z

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gemini-code-assist · 2025-09-26T12:43:02Z

Summary of Changes

Hello @vaskkey, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves an issue where the autolinking mechanism failed to correctly prepend the "http://" protocol to URLs that began with a case-insensitive "www." prefix. By updating the tokenizer's logic to perform a case-insensitive check, the system now ensures that all variations of "www." (e.g., "Www.", "WWW.") are properly recognized and converted into fully functional, clickable links, preventing broken redirections.

Highlights

Case-insensitive www. prefix handling: The pull request modifies the autolinking logic to correctly prepend "http://" to URLs starting with "www." regardless of their casing (e.g., "Www.", "WWW.").
Fix for broken autolinks: Previously, only lowercase "www." was recognized, causing links like "Www.foo.com" to not have "http://" prepended, resulting in incorrect redirection.
Implementation detail: The fix involves changing a strict equality check (cap[1] === 'www.') to a case-insensitive comparison (cap[1]?.toLowerCase() === 'www.') in src/Tokenizer.ts.
Test coverage: New test cases have been added to test/specs/new/autolinks.md and test/specs/new/autolinks.html to validate the corrected behavior for various www. casings.

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Code Review

This pull request fixes an issue where www. prefixes in URLs were not handled case-insensitively for autolinking. The change correctly identifies prefixes like Www. and prepends http://. The implementation is correct according to the goal, and new tests are added to cover the case-insensitive scenarios. I have one suggestion for improvement regarding URL normalization for better standards compliance.

gemini-code-assist · 2025-09-26T12:44:55Z

src/Tokenizer.ts

        } while (prevCapZero !== cap[0]);
        text = cap[0];
-        if (cap[1] === 'www.') {
+        if (cap[1]?.toLowerCase() === 'www.') {


This change correctly handles case-insensitive www. prefixes. However, the generated href preserves the original casing of the domain (e.g., http://Www.foo.com).

According to RFC 3986, the host component of a URI is case-insensitive. It is a best practice to normalize it to lowercase in the href attribute for consistency and to prevent potential issues. The visible link text should preserve the original user input.

You could consider updating the logic inside this if block to normalize the domain part of the URL. Here's a possible implementation:

// inside the if (cap[1]?.toLowerCase() === 'www.') block const pathStartIndex = cap[0].search(/[\/?#]/); const domain = pathStartIndex === -1 ? cap[0] : cap[0].substring(0, pathStartIndex); const path = pathStartIndex === -1 ? '' : cap[0].substring(pathStartIndex); href = 'http://' + domain.toLowerCase() + path;

If you apply this change, please remember to update the corresponding test case in test/specs/new/autolinks.html to expect a lowercase href.

UziTech · 2025-09-26T14:55:09Z

Autolink is a GFM extension so we want it to act the same as GitHub and it looks like GitHub doesn't allow the www to be case insensitive.

www.example.com
Www.example.com
WWW.example.com

If this is something you want you can create a custom extension

vaskkey · 2025-09-26T20:09:23Z

@UziTech In that case I could probably configure the autolink to be a bit stricter than it is right now. because currently for Www.example.com marked generates <a href="Www.example.com">Www.example.com</a> which is neither a good link nor a GitHub way of parsing links

UziTech · 2025-09-27T01:09:56Z

Good call. Ya that sounds good. We want it to be the same as GitHub

vaskkey · 2025-09-29T17:40:23Z

Closing this PR, Github-like implementation here: #3770

fix: Handle case-insensitive www prefix

6d73f9c

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fix: Handle case-insensitive `www.` prefix #3769

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fix: Handle case-insensitive www. prefix #3769

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vaskkey commented Sep 26, 2025

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fix: Handle case-insensitive `www.` prefix #3769

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