Hi, As of March 31 I intend to start a rollout of 50% of Beta 138 to remove UA styles for h1 in article, aside, nav, section on desktop. We will monitor web compat reports to evaluate impact. If it goes well, the plan is to roll out to 5% of Release 138 and then increase to 50%, and if it goes well, increase to 100% and let the change ride the trains for all platforms.
Status in other browsers is that they are interested in following our lead ( 1 <https://github.com/whatwg/html/issues/7867#issuecomment-2125552252>, 2 <https://github.com/whatwg/html/issues/7867#issuecomment-2124317504>). Chromium has also deprecated <https://issues.chromium.org/issues/394111284> this, which makes the issue surface for web developers in Chromium's console as well as impacting the score in Lighthouse <https://github.com/whatwg/html/issues/7867#issuecomment-2711538791>. *Bug to remove*: https://bugzilla.mozilla.org/show_bug.cgi?id=1885509 *Spec issue*: https://github.com/whatwg/html/issues/7867 *Rollout for Beta*: https://experimenter.services.mozilla.com/nimbus/remove-ua-styles-for-h1-headings/summary *Rollout for Release*: https://experimenter.services.mozilla.com/nimbus/remove-ua-styles-for-h1-headings-release/summary *Pref*: layout.css.h1-in-section-ua-styles.enabled (false means the UA styles are removed) *Compat analysis*: - March 2024: https://github.com/whatwg/html/issues/7867#issuecomment-1977647444 - January 2025: https://github.com/whatwg/html/issues/7867#issuecomment-2595987424 We have a warning in the devtools console since 136 when a page has a h1 in article, aside, nav, or section, and no author-origin font-size or margins specified. The pref has been false in Nightly since March 2024, with only one web compat issue <https://bugzilla.mozilla.org/show_bug.cgi?id=1886480> reported (the site was fixed). Rationale and context for this change: - h1 was specified to have automatic heading level based on the number of ancestor sections (or aside, article, nav). - The default rendering was specified to (roughly) match, such that <section><h1> would have the same font-size and margin as h2 - The default rendering was implemented in browsers, but not the heading level in the accessibility tree. - Websites started to use sectioning elements, but didn't expect automatic heading levels. It was not possible for browsers to change that without breaking user expectations. - The automatic heading level (a.k.a. the outline algorithm) was dropped from the spec, but the default UA stylesheet remained. This is what we're trying to remove now. Advice for web developers: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/Heading_Elements#specifying_a_uniform_font_size_for_h1 cheers, -- Simon Pieters https://www.mozilla.com/ -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/a/mozilla.org/d/msgid/dev-platform/CAC7mYC4dY4LkjOxS_rv-zvFpX%3DSUqmFUQN-bKQCSS9psRAvE5g%40mail.gmail.com.
