The RFC 8949 describes the Concise Binary Object Representation (CBOR). It's a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation.
While certainly interesting, currently this appears to be, as you state yourself, not something we could test support for, therefore not (yet) fitting for caniuse?
The RFC 8949 describes the Concise Binary Object Representation (CBOR). It's a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation.
As far as I know, it's not yet supported in browsers (on 2021-12-14) but at least there are discussions in Chrome.
Edit: RFC 7049 was deprecated, replacing by RFC 8949.