Basically smaller file sizes than JPEG at the same quality and it also automatically loads a lower quality version of the image before it loads a higher quality version instead of loading it pixel by pixel like an image would normally load. Google refuses to implement this tech into Chrome because they have their own avif format, which isn’t bad but significantly outclassed by JPEG-XL in nearly every conceivable metric. Mozilla also isn’t putting JPEG-XL into Firefox for whatever reason. If you want more detail, here’s an eight minute video about it.
Insane that I had to scroll this far down to find Samus mentioned