It may very well be the case that caniuse doesn't bother tracking WICG standards, in which case, please close this issue and disregard it.

Otherwise, major browsers have already implemented this feature which allows greater levels of zstd and brotli compression via compression dictionaries. It's a new standard that has been under discussion and in development for about one or two years. I understand that it was released in Chrome 130 just a couple days ago.

See https://datatracker.ietf.org/doc/draft-ietf-httpbis-compression-dictionary/ and https://github.com/WICG/compression-dictionary-transport