Well, no it wasn't sarcasm... if Twitter can offload image attach and crop entirely onto the client, I figure they would be doing that. Certainly their frontend

Well, no it wasn't sarcasm... if Twitter can offload image attach and crop entirely onto the client, I figure they would be doing that. Certainly their frontend engineers understand how to. But they must have some reasons for involving the server. Because they do! If you go attach an image to a new tweet, you will see it gets uploaded right then and there, whether or not you ever hit post. Who knows what happens from there. Allowing clients to demand more crop work, at will, on top of the one that is automatic seems like it would have some implications at twitter's scale. At the very least, it would probably undo some optimizations they've made around image handling.