This change has been rolled out to 50% of beta 138 for the past two weeks. No reported regressions so far due to this change.
I have published an article on the MDN Blog <https://developer.mozilla.org/en-US/blog/h1-element-styles/> which received some comments on Hacker News <https://news.ycombinator.com/item?id=43649853>. After taking the feedback into consideration, the rollout plan is adjusted slightly: - Increase the rollout on 138 beta to 100% (asap), so that web developers who test in beta have a chance to see the change before it reaches users on release. - Only roll out to 10% of users on release, instead of 50%. This should be sufficient to make a decision to ship. cheers, On Mon, Mar 24, 2025 at 9:57 PM Simon Pieters <[email protected]> wrote: > 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/ > -- 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/CAC7mYC5-wqRS1yX%3DVB9DoYT%3D8zOPJ-svykPzRvrAWwWSzkA0yg%40mail.gmail.com.
