- Mac OS, iOS, and Safari support JPEG-XL
- Windows has first party JPEG-XL support as of this year (admittedly it's opt in rather than default)
- Essentially every major image processing app, editor, or drawing app supports JPEG-XL
- Firefox has preliminary support for JPEG-XL gated behind a feature flag and the nightly release.
- The JPEG-XL team is writing a direct port of the reference libjxl library into rust[1]. There already exists a third party rust port by some of the mainline contributors and it has ironed out a lot of the issues with the porting process prior to this mainline port. This first party rust port is intended to be gradually brought up to a hardened, production ready state.
- Mozilla has stated they have no objections to fully adopting JPEG-XL in Firefox once the rust port is production ready [2].
The last major barriers other than getting the rust code production ready will be chrome and android's first party support/adoption.
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TLDR: JPEG-XL is very much not dead and instead people are nose down working hard to continue pushing its adoption forward.
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I was not aware of this. Also judging by this and the sibling comments, it looks like the momentum didn't die despite Google's apathy. Hopefully the fact that their own team is now developing the rust port, as well as the growing support in other platforms, is enough to make Google reconsider its choices.