Since the bug is closed and we can no longer reply, i'll drop brief comments here: 1) We lack data showing that WebP is significantly enough better than JPEG i

Since the bug is closed and we can no longer reply, i'll drop brief comments here: 1) We lack data showing that WebP is significantly enough better than JPEG in terms of compression. [...] If we omit Google numbers (that this blog post and the ones before reported), Facebook reported 20% saving as a starting point for mobile (http://internet.org/efficiencypaper http://internet.org/efficiencypaper). the Mozilla bug has good number reported (Netflix, Akamai and other CDNs, etc...) inbetween the noise. 2) Last time I checked, it was not possible to create large WebP images. I couldn't encode a ~20 megapixel image. This was fixed in libwebp0.4.0. (but i hope no web site is going to send me a 20megapixel image while i'm on my phone) 3) I suspect it's unlikely that MS will agree to include WebP support in IE, maybe ever. Not having MS on board, given their market share, is problematic. It means lots more header/UA checks and double solutions for every use of WebP, possibly for a long time. UA detection are here to stay for quite some time anyway, before all current browser versions are retired (if that ever happens). Responsive web put the load on server logic, then. 4) I haven't done extensive testing on this yet, but word is that WebP compression advantages fall off when an image gets larger than about 500x500 pixels. This might be why we see WebP perform a bit worse on the Tecnick image set (~1200x1200) than the Kodak set (~768x512) in my last study. This may also be impacting other peoples' tests. I'm curious to know more about this. VP8 uses 4x4 transform, not 8x8. That's the main difference with jpeg that limit the efficiency at high dimensions. Although 500x500 seems a bit low. Let's also note that your study was also using a downsampling version of the SSIM metric, which could be interacting favorably with jpeg's larger transform block. 5) Users can't do much with WebP images today if they save them. As Facebook learned, this frustrates users. As this is a bit of a chicken-and-egg problem it's less important, but it is a consideration. That was mostly an app problem. Android faces the same problem with the data proxy mentioned in the blog, but this is taken care of client-side. skal