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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/…
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Firefox for Web Developers retweeted
When and how CSS custom property values are calculated might not be what you expect, and it has a big impact on your styles…
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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…
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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…
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Firefox for Web Developers retweeted
📝 When and how CSS custom properties are calculated might not be what you expect, and it has a big impact on your styles.
Here's how it works: jakearchibald.com/2026/css-c…
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CSS sibling-count() and sibling-index() are newly available across engines! Here's how they work:
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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…
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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.…
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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…
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Chrome also has an Intent to Ship, so support should land in both browsers within a week of each other groups.google.com/a/chromium…
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What should happen with text-box-trim and margin-trim when it comes to negative values? Do negatives 'trim'?
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CSS issue: github.com/w3c/csswg-drafts/…
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CSS text-box is newly baseline, and it's solves a common text layout issue. Here's how it works: instagram.com/reel/DcORXuGFN…
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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/…
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