[modeless]

I'd rather have JPEG XL personally. The other one that's really cool is Basis Universal, which is unique among compressed image formats in that it decodes directly to a GPU compressed texture in VRAM, resulting in way less memory usage and bandwidth consumption when the image is displayed. That's right, it remains compressed even as you view it!

[jjcm]

The reason why I'm mainly excited about .avif is that it'll run on the same hardware that decodes .av1 files. Means encoders will very easily be hardware accelerated - great for services or bulk encoding projects.

[astrange]

Hardware decoders tend to have strict limits on things like picture size, which video complies with and random still images often don't. So compatibility is not guaranteed.

Neither is quality of course. Video encoders aren't always tuned for still images and it's even harder to tune a hardware encoder.