macOS 14 / Safari 17.6 shows static pics, but no animation.
Honestly, I wish all animated image formats would just die. They are an inefficient way to animate images, because they only use intra frames. H.264, H.265 or AV1 should be used for animations. Fortunately, Safari can display video files in <img> or CSS images, which makes all animated image formats unnecessary.
Yes, it does. It's a limited sort of animation like GIFs were; JPEG XL is not derived from video codecs like WebP, AVIF, and HEIF are, where those formats include "animation" by really breaking out of being a subset and just being the regular intraframe video codec.
The Firefox and Chrome teams will likely get around to adding it eventually, but it's a real shame that they've both chosen to defer it. Normally Safari is the one lagging behind on web standards but somehow it's ended up being the one to lead the charge here.
https://jpegxl.info/test-page/
At the bottom of the page it has animation demonstration, that doesn’t appear to work on my iPhone 13 Pro.
Does JPEG-XL really include animation support?