I would be more concerned about the memory consumption (especially on mobile). On ios in particular I recall[1] something about jpg taking up significantly mor

I would be more concerned about the memory consumption (especially on mobile). On ios in particular I recall[1] something about jpg taking up significantly more than their file size in memory, due to decoding the image. png's don't suffer from that (an ios optimization for pngs or something), but they tend to be overall larger for big files (retina size). I would think webp.js would be even worse off than jpg in regard to memory usage for mobile devices. (note: this is just a guess/hunch though. I saw no data one way or the other on the linked post, nor on the libwebp site). [1]: Maybe a fellow HN'er knows more about this particularity with regard to ios image memory consumption. edit: found this: http://cubiq.org/testing-memory-usage-on-mobile-safari http://cubiq.org/testing-memory-usage-on-mobile-safari which appears to rebut the jpg/png memory discrepancy. Perhaps our particular app was doing something odd with the jpg images we were testing, that was causing the additional memory usage. Maybe it had to do with loading in the actual jpg decoding code itself (png perhaps already loaded?). edit2: this article seems to confirm it: http://mobile.tutsplus.com/tutorials/mobile-design-tutorials/mobile-design_png-or-jpg/ http://mobile.tutsplus.com/tutorials/mobile-design-tutorials... subtext: test test test! :P