Shared Dictionaries: compression that keeps up with the agentic web

This post introduces Cloudflare's upcoming support for shared compression dictionaries, a feature based on RFC 9842. It details the problem of increased web page weight and deployment frequency leading to caching inefficiencies. The solution involves delta compression where the browser's cached version of a resource acts as the dictionary for subsequent requests. Cloudflare's implementation will start with passthrough support for `Use-As-Dictionary`, `Available-Dictionary`, and `dcb`/`dcz` content encodings, with cache keys varying on these headers. Early testing showed significant bandwidth savings.