Firefox 157 will include JPEG XL by default on all platforms

Firefox 157 will ship JPEG XL enabled by default on every platform.

That makes two of the three browser engines. Safari has had it since 2023; Chromium removed its implementation and hasn't come back. So the practical answer for anyone serving images doesn't change much on its own, JXL becomes a source inside a picture element with a fallback behind it, not a replacement for what you already encode.

What does change is the argument. The case against JXL has mostly been "nobody ships it," which is self-fulfilling and hard to push back on. A default-on decoder in Firefox across all platforms turns that into an actual share of your traffic, and a number is something you can take to whoever owns the image pipeline.

I'd add the source tag now and let the fallback carry everyone else.

https://news.ycombinator.com/item?id=49437946