Right now, Mastodon downloads local copies of:

• avatar
• header
• status media attachments

On these local copies, Mastodon can perform operations like resizing, optimizing, creating thumbnails that fit Mastodon's UI - because the origin of the content can provide media in super large sizes that would severely impact end-user's bandwidth and browser performance if just displayed verbatim.

Moreover, bandwidth is not always cheap - it is capped to something like 1TB/mo on DigitalOcean, and is super expensive on Amazon S3, so hotlinking images and videos would severily impact owners of small instances, when lots of users of large instances would view their content from their public timelines (or even just home timelines through boosts). It does feel fair that an instance's admin is responsible for serving content to their own users, rather than also to users of other instances, which should be their admins' responsibilities.

However, this has storage and legal implications. I would like to hear your thoughts on how this can be improved.