JPEG XL has arrived on the web, but how does it stack up against AVIF? https://jakearchibald.com/2026/jpeg-xl-vs-avif/

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.

https://interop-rank.fxdx.dev/

I'm really glad we're running this again. It helped us prioritise a lot of work this year.

The previous method was counting 👍 on GitHub issues, which (imo) is too easily gamed, either intentionally or unintentionally.

https://mastodon.social/@firefoxwebdevs/117405530050775102

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.

https://interop-rank.fxdx.dev/

After careful consideration and a look at where the industry is spending it's funding we've decided to pivot #FFConf in a "new" direction.

I present to you: https://ffconf.ai/

Please share with bots and humans alike.

I've been playing around with HDR images on the web. It seems that, for AVIF (the only web format that supports high bit depth and gain maps), gain maps add a lot of overhead. On the web it'd be much better to use <picture> to serve the right image for the screen.

cjxl doesn't support gain maps yet, and neither does jxl-rs, but it'll be interesting to see if it has this same overhead problem. I suspect it will.

I've proposed "progressive image rendering" as a focus area for Interop 2027, so we can get progressive JPEG XL support in Safari, and progressive AVIF support in both Safari and Firefox. https://github.com/web-platform-tests/interop/issues/1459

Two weeks from now Fronteers Dark Mode will happen in Dordrecht in The Netherlands. There are still a few tickets left. Be quick ⚠️

Join us for an afternoon and evening of great talks. With a spectacular line up: Anjana Vakil, @tunetheweb, @Cyd, @csswizardry and @heydon.

And let's not forget our amazing MC:
@jaffathecake.

Tickets are just €99 ⭐️ and a two-course dinner is included as well 🍽️ @fronteers members will get a 50 euro discount.

🎟️ www.fronteersconf.org

This is a great article. I've always been sus about the hype around JPEG XL, as it never stacked up when I actually tested it with web use-cases.

https://giannirosato.com/blog/post/case-against-jxl/

When and how CSS custom property values are calculated might not be what you expect, and it has a big impact on your styles…

The CSS progress() function is now in all major engines! Here's how it works:

Playing around with an idea: responsive code.

The build script creates up to 5 versions of each code sample using Prettier, and a container query displays the right one.

Brotli means the filesize overhead is very small.

Live demo: https://jakearchibald.com/2026/css-custom-property-compute-time/

CSS attr() now works on all properties in Firefox 155. Here's how it works, and how to get the most out of it:

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()
🎉 CSS alpha()
🎉 Promise.allKeyed() and allSettledKeyed()
🎉 Wasm wide arithmetic
🎉 Lots of new WebTransport stuff

…And more!

https://developer.mozilla.org/en-US/docs/Mozilla/Firefox/Releases/155

📝 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: https://jakearchibald.com/2026/css-custom-property-compute-time/

📝 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: https://jakearchibald.com/2026/css-custom-property-compute-time/

CSS sibling-count() and sibling-index() are newly available across engines! Here's how they work:

It's really weird that the response to JPEG XL shipping is "yesss fuck WebP!"

Like, we've had AVIF for years, and it outperforms JPEG XL in almost all web use-cases.

JPEG XL is slated to ship in Firefox 157 next month! Here's how we're shipping it safely… https://hacks.mozilla.org/2026/08/intent-to-ship-jpeg-xl/

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.

https://groups.google.com/a/mozilla.org/g/dev-platform/c/3YMV4MS34KA