impressive:

Lossless JPEG Re-compression

An incredibly unique JPEG-XL feature that no other codec can currently offer competition to is lossless JPEG re-compression, or the ability to take a JPEG input and provide an output with a smaller filesize (on average, 20% smaller) that is pixel-for-pixel identical. This is why companies like Meta have endorsed JPEG-XL, as it offers a path forward for the existing JPEGs on the Internet.

Apple really gave JXL the boost it needed. A part of me deep inside hopes that Apple switches to JXL & leapfrogs the whole gain map JPEG thing going on in Android land currently, then Android OEMs can switch to JXL too. HEIC is not & will never be compatible enough, and the royalties ruin it.