matrix-doc/proposals/2703-media-id-grammar.md

MSC2703: Media ID grammar

Media IDs are the identifiers accompanied by a domain in an MXC URI: mxc://domain/mediaId

Implementations currently rely on assumptions and commonality for media IDs due to lack of specification.

Proposal

Media IDs must be treated and represented as opaque identifiers. Only characters in the RFC 2986 Unreserved Characters set can be used.

Media IDs must be less than 255 characters.

Potential issues

The character set could be overly restrictive, however in practice at 255 characters there's a very reasonable number of possible identifiers. If a server does find itself running out, we can adjust the spec or they could deploy a secondary server to handle even more media.

Alternatives

We could go without this specification, but that sounds very unfortunate.

Security considerations

None applicable.

Unstable prefix

None required.