I don't believe any platforms or browsers have enabled JPEG-XL support yet, so right now you'd need to ship the decoder yourself anyway.
But, it's at least as much better than WebP as WebP was better than JPEG. And unlike HEIC, web browsers are considering supporting it, though AVIF is currently ahead of JPEG-XL in browser support.
JPEG-XL also currently beats HEIC and AVIF at medium to high quality, but it's a fair question just how much that's intrinsic to the format and how much that is from libjxl's tuning focus being at those quality levels; AV1 and HEVC encoders have mostly focused on lower bitrates in the range that video would use.
JPEG-XL is the ~best lossless image format currently available, though.
> though AVIF is currently ahead of JPEG-XL in browser support.
It certainly looks like AVIF is ahead because it has landed in and Firefox and Chrome, but it's blocked in Safari by a required OS change[0] (iOS/macOS support if I understand the comment correctly?). Additionally, there's no implementation in Edge (even though it's chromium)[1]. Sorry, I wish I had more details but I'm not sure where to look to find a status update on that.
Meanwhile, JPEG-XL has support behind a feature in every major browser except Safari[2]. As you and others have noted, there seems to be a lot of buzz and excitement around JPEG-XL throughout the ecosystem. The webkit folks seem to be making an effort to get the ball rolling[3]. I might be misinterpreting something but it all looks very encouraging at any rate. It almost seems like it might gain wide support in Firefox and Chromium (Chrome & Edge) around the same time with Webkit following (hopefully) closely thereafter. Heck, I don't see why Webkit doesn't just abandon AVIF and focus on rolling out JPEG-XL.
But, it's at least as much better than WebP as WebP was better than JPEG. And unlike HEIC, web browsers are considering supporting it, though AVIF is currently ahead of JPEG-XL in browser support.
JPEG-XL also currently beats HEIC and AVIF at medium to high quality, but it's a fair question just how much that's intrinsic to the format and how much that is from libjxl's tuning focus being at those quality levels; AV1 and HEVC encoders have mostly focused on lower bitrates in the range that video would use.
JPEG-XL is the ~best lossless image format currently available, though.