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Yes but behind a Flag. With default settings, it hasn't landed in any browser yet: https://caniuse.com/jpegxl

I hope that Safari does not take as long to implement it as with WEBP...

I doubt it will be enabled by default until it reaches version 1.0, it is currently at 0.3 IIRC

This is only 1 browser with 3 distributors.

Firefox is a very different browser. Edge shares its base with Chrome, and that's derived from WebKit.

firefox is chrome distribution? that's new to me