Official Firefox account for people who build on the web. Learn about the things we're working on to grow and improve the web platform.
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Joined June 2009
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Firefox 159 has landed! This is a pretty big one for web dev stuff:
🎉 CSS scroll-driven animations, both scroll() and view().
🎉 Scoped custom element registries.
🎉 Streaming sanitization of HTML.
And more! developer.mozilla.org/en-US/…
Scoped custom element registries are newly available in all major engines, meaning multiple implementations can use the same tag name without clashing. Here's how they work:
MDN docs: developer.mozilla.org/en-US/…
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MDN docs: developer.mozilla.org/en-US/…
And Bramus' YouTube series: youtube.com/playlist?list=PL…
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What should we ship in 2027? Rank your favourite features & create your wishlist: interop-rank.fxdx.dev/
Firefox 158 landed today! For web devs:
🎉 JPEG XL support, including full progressive rendering.
🎉 'navigate' on notifications, so they can go to a URL without firing events.
🎉 WebGPU's float32-blendable
🎉 WebGL's EXT_polygon_offset_clamp
And more!
developer.mozilla.org/en-US/…
We've loved seeing folks post their rankings, so we've added a share button!
You can either share your list via the site directly, or copy your list as markdown/html for your own blog.
interop-rank.fxdx.dev/
What do you want us to work on in 2027?
Here's a web app where you can rank the Interop proposals you care about, giving us data we can use to prioritise feature development.
interop-rank.fxdx.dev/
Firefox 157 has landed, and includes a couple of useful CSS features:
🎉 at-rule() in @supports - limit rules to browsers that support a given at-rule.
🎉 overscroll-behavior: chain - allow chained scrolling without overscroll effects.
…And more! developer.mozilla.org/en-US/…
When and how CSS custom property values are calculated might not be what you expect, and it has a big impact on your styles…
Full docs on MDN: developer.mozilla.org/en-US/…
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Interop 2027 is open for proposals! Is there a well-tested feature that you'd like to see cross-browser focus on next year? Submit it here: github.com/web-platform-test…
CSS attr() now works on all properties in Firefox 155. Here's how it works, and how to get the most out of it: instagram.com/reel/Dc05U1ilb…
Major versions of Firefox now land every two weeks, so Firefox 155 dropped today with web platform features including:
🎉 Fully typed CSS attr()
🎉 CSS progress()
🎉 Promise.allKeyed() and allSettledKeyed()
🎉 Lots of new WebTransport stuff
…And more!
developer.mozilla.org/en-US/…
And the full docs on MDN: developer.mozilla.org/en-US/…
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JPEG XL is slated to ship in Firefox 157 next month! Here's how we're shipping it safely… hacks.mozilla.org/2026/08/in…
Intent to ship: JPEG XL! This will be on-by-default in Firefox 157, which should become the main release version at the end of September.
This includes key JPEG XL features like progressive rendering.
groups.google.com/a/mozilla.…
In a JPEG XL compatible browser (like Firefox Nightly), test how it renders progressively by moving the slider in this demo: random-stuff.jakearchibald.c…
What should happen with text-box-trim and margin-trim when it comes to negative values? Do negatives 'trim'?
CSS issue: github.com/w3c/csswg-drafts/…
![[css-inline-3] Does `text-box-trim` remove negative leading? · Issue #14328 · w3c/csswg-drafts](https://pbs.twimg.com/card_img/2118641773031342080/0CtbpAyZ?format=jpg&name=800x419)
CSS text-box is newly baseline, and it's solves a common text layout issue. Here's how it works: instagram.com/reel/DcORXuGFN…
Full docs on MDN: developer.mozilla.org/en-US/…
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Firefox 154 landed today, and brings with it some great web platform features:
🎉 CSS text-box
🎉 CSS sibling-index() and sibling-count()
🎉 JS Iterator methods like chunks, window, includes, & join
🎉 HTTP No-Vary-Search
…And more! developer.mozilla.org/en-US/…