Web-Facing Change PSA: Case-sensitive anchor name matching in quirks mode

[Chromestatus]

Contact emails

stephan...@microsoft.com, leo...@microsoft.com

Specification

https://html.spec.whatwg.org/multipage/browsing-the-web.html#find-a-potential-indicated-element

Summary

Anchor name matching for fragment navigation will become case-sensitive in quirks mode, matching the behavior in standards mode. Previously, navigating to #Foo could match <a name="foo"> in quirks mode. This aligns Chromium with Safari, Firefox, and the HTML specification, which do not perform case-insensitive matching.

Blink component

Blink>DOM

Web Feature ID

Missing feature

Risks

Interoperability and Compatibility

Very low risk. Use counter data shows the case-insensitive fallback fires on ~0.00015% of page loads. Both Safari and Firefox already ship case-sensitive matching in quirks mode, so this change improves interop. The behavior change is guarded behind the CaseSensitiveAnchorMatching runtime flag for easy rollback

Gecko: Shipped/Shipping

WebKit: Shipped/Shipping

Web developers: No signals

Other signals:

Ergonomics

None

Activation

Low risk. Pages in quirks mode (no DOCTYPE) that rely on case-insensitive anchor matching (e.g., href="#Foo" targeting <a name="foo">) will need to update their fragment links or anchor names to use matching case. Use counter data shows this affects approximately 0.00015% of page loads

Security

None

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

No information provided

Debuggability

No DevTools changes needed

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

Yes
https://chromium-review.googlesource.com/c/chromium/src/+/7727981/14/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/scroll-to-fragid/scroll-to-anchor-name-quirks-case.html https://wpt.fyi/results/?label=master&label=experimental&aligned&q=html%2Fbrowsers%2Fbrowsing-the-web%2Fscroll-to-fragid%2Fscroll-to-anchor-name-quirks-case.html

Tracking bug

https://issues.chromium.org/issues/40829784

Measurement

UseCounter for AnchorCaseSensitiveMatch: https://chromestatus.com/metrics/feature/timeline/popularity/5784 UseCounter for AnchorCaseInsensitiveMatch: https://chromestatus.com/metrics/feature/timeline/popularity/5785

Estimated milestones

Shipping on desktop	160
Shipping on Android	160
Shipping on WebView	160

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5085237991309312

This intent message was generated by Chrome Platform Status.