there are two solutions
https://github.com/nostr-protocol/nips/blob/master/94.md
and blossom
https://github.com/nostr-protocol/nips/blob/master/B7.md
as far as I know most clients use blossom
Discussion
Okay interesting thank you. I'm curious about running a blossom server. Can this really scale as nostr grows? I'm imaging at some point in the future there ought to be some incentive to hold all this data. Like each upload needing some zaps with it.
I think it can scale, because it's similar to a cdn with more logic on the client side.
And yeah you are probably right about an incentive, this could be money or other things like certain groups caring about certain data.