I highly doubt that is what's happening. More likely the server is serving a webp under a .png filename or something.
replyI have observed the behavior you suspect many times.
replyI don't think that's firefox doing it? I'd guess it's some CDNs doing the conversion. Or the URL says .jpg but when you look at the mimetype sent by the server it's actually webp. Extentions are meaningless for browsers.
replyIt's not Firefox, it's the server. Edit and resend the request with header "Accept: image/jpeg" only and you'll most likely get a JPEG file.
replyThat seems more likely. I still hate webp.
replyDoes it actually request the image that it already downloaded again to save it to a file? Seems rather silly?
replyNo, the server is just sending the file named 'foo.jpg', but encoded as a webp with webp mime type, so when you save the file it defaults to the webp extension cause it ends up treating the filename as a blob of text without an expected extension for the file type.
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