[blopker]

Google answers this question in the FAQ: https://developers.google.com/speed/webp/faq#does_webp_suppo...

But in my experience, webp is better enough that the whole file loads around the same time the jpg progressive loading kicks in. Given that progressive jpgs are larger than non progressive (so not a 'free' feature), jpg is just a waste of bandwidth at this point.

[butvacuum]

That link doesn't address my point at all. If you have 1000 photos in a scrolling gallery there's no lossy format besides JPEG that allows you to grab just enough of the file to render a thumbnail. This has Major bandwidth, Storage, Compute, and UI responsivness implications.