Brotli's baked-in dictionary always irked me because it's forever fixed and can't be updated (not that I'm implementing new hypermedias on a weekly basis but still). I'd much rather see broad adoption of plain 'Content-Type: zstd` implemented with no dictionary, and later go through a standards process to add named content-specific dictionaries like `Content-Type: zstd-web` or `zstd-cn` or whatever.

Edit: Actually this is already considered in RFC-8878 [0]. The RFC reserves zstd frame dictionary ids in the ranges: <= 32767 and >= (1 << 31) for a public IANA dictionary registry, but there are no such dictionaries published for public use yet.

[0]: https://datatracker.ietf.org/doc/html/rfc8878#iana_dict