every client should do that but that's not a solution that works. there are too many clients that don't care.
Discussion
hodlbod could explain Postell's Law for this case
it's really nbd tho, seriously, rescaling images deterministically and distributed attestations would be enough to allow just a few to cache it while others just store and share the scaled down version which refers back to it
Additionally, who determines what size is ok and what is not? If you have plenty of bandwidth 50MB might even be acceptable whereas in some cases 50KB might be pushing the limits already, so any solution can only be on the receiving end i think.
If you do not want to waste large amounts of bandwidth the receiver needs controls for that. Either block it or do something like nostr:nprofile1qqsyeqqz27jc32pgf8gynqtu90d2mxztykj94k0kmttxu37nk3lrktcpz4mhxue69uhhyetvv9ujummjd3ujuer9wchszxmhwden5te0daexc7fdwfjkccte9e5k6ampd3jzuet49uq3wamnwvaz7tmjv4kxz7fwdehhxarj9e3xzmny9u5f9yd3 is suggesting. I would settle for simply not showing and use a placeholder or something.
often you don't know how large a file is before you download it
make Content-Length mandatory in spec. make clients ignore images that do not follow spec.
There’s no spec for a link …
that would require changing specs of kinds 0, 1, 20 etc.
"images should be only loaded from HTTP servers that return Content-Length HTTP header or specify Content-Length in imeta metadata"
This does not belong in specs because it's totally dependent on the end user. It belongs in a client. If you can't determine content length the client should offer you the option to not download it.
There is no one-size-fits-all possible here. On my home connection i wouldn't even be able to tell the difference between 50MB or 50KB. If you are somewhere with near zero bandwidth you should reconsider your priorities and maybe download zero external links and settle for notes only.
Yeah slow connection or text only mode
You can’t enforce this and there’s no such thing for a random image link … it just wouldn’t make much of a difference I’m afraid