It is supported by Adobe, included in Safari 17, is behind a flag in Firefox, and was behind a flag in Chrome too until they idiotically chose to remove it despite severe pushback from the community. My take is that it will be one of the most-popular image formats in the coming decade.
Their decision is schizophrenic: the JPEG XL format is a combination of two technologies: PIK (developed by Google) and FLIF (developed by Cloudinary) - one of them developed by Google. It is entirely sensible for them to reverse their decision, which came before Safari announced the format would be supported.
Adobe is already supporting the format, and many image editors / browsers are including it.
Finally, adding a WASM polyfil to your website would still yield many benefits, enough to outweigh not-100%-yet-support-by-browsers.
From my very very limited understanding, the amount of influence webp (compared to even say AVIF) people have seems disproportionate compared to how useful it's been.
"Considering JXL has been endorsed by Facebook, Adobe, Intel and the Video Electronics Standards Association, The Guardian, Flickr and SmugMug, Shopify, the Krita Foundation, Serif Ltd, Gaia Sky, and many more, the market is most certainly interested. My current optimistic hope is that JXL takes off outside the web among professionals working with tools like the Adobe suite or alternatives, and camera manufacturers, smartphone OEMS, and others take notice & begin to think about JXL more seriously. The benefits cannot be ignored, and it is (in my opinion) the only image format that is in every way superior to JPEG & offers a concrete future for the many existing JPEGs on the Web & beyond."
https://jpegxl.info/
It is supported by Adobe, included in Safari 17, is behind a flag in Firefox, and was behind a flag in Chrome too until they idiotically chose to remove it despite severe pushback from the community. My take is that it will be one of the most-popular image formats in the coming decade.