> I think Google’s result of 25-34% smaller files is mostly caused by the fact that they compared their WebP encoder to the JPEG reference implementation, Indep

> I think Google’s result of 25-34% smaller files is mostly caused by the fact that they compared their WebP encoder to the JPEG reference implementation, Independent JPEG Group’s cjpeg, not Mozilla’s improved MozJPEG Well, MozJPEG didn’t exist until four years after WebP, so I suspect that might explain why.