Profile: 0dc595a6...

$ curl -I

...

content-length: 29297

ignore images that are too large based on http headers content-length

ignore gifs because gif is stale file format

when adding profile pic, make client side compression to eg 500x500 webp

further optimization:

there could be two profile pic files. one small, and one larger when you open profile or click to view full size image

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you cannot expect any specific behaviour from users. anyone can set any size of profile pic. you can however make clients not to download those.