Yeah it’s very common for CDNs to transcode images (convert them to a different format) to save bandwidth. Your browser or app tells the server which image formats it supports using the Accept HTTP header, and the server returns the image in the best format it supports. There’s been significant improvements to data compression technology in the last 20+ years, and an AVIF file is usually around 50% the size of a comparable JPEG file of similar quality.
Cloudflare does this (although I’m not sure if it’s only a paid feature or if it’s available on free accounts too), and major services like Google, Facebook, Instagram, etc do it too. At those scales, halving the amount of bandwidth used by images is a significant saving.
If an app gets an image format it doesn’t support, it’s likely not setting the Accept header correctly.
Edit: There’s also JPEG XL which is essentially supposed to be like “JPEG 2.0”, but it’s not widely supported yet.
.zip uses an image proxy server which might be doing the conversion automatically.
Yeah it’s very common for CDNs to transcode images (convert them to a different format) to save bandwidth. Your browser or app tells the server which image formats it supports using the
AcceptHTTP header, and the server returns the image in the best format it supports. There’s been significant improvements to data compression technology in the last 20+ years, and an AVIF file is usually around 50% the size of a comparable JPEG file of similar quality.Cloudflare does this (although I’m not sure if it’s only a paid feature or if it’s available on free accounts too), and major services like Google, Facebook, Instagram, etc do it too. At those scales, halving the amount of bandwidth used by images is a significant saving.
If an app gets an image format it doesn’t support, it’s likely not setting the Accept header correctly.
Edit: There’s also JPEG XL which is essentially supposed to be like “JPEG 2.0”, but it’s not widely supported yet.