Shared Dictionaries: compression that keeps up with the agentic web

This Cloudflare blog post explains how shared compression dictionaries (delta compression) will reduce redundant bandwidth by compressing new resource versions against previously cached client versions. It describes what shared dictionaries are, the historical security lessons from SDCH (CRIME/BREACH), the RFC 9842 improvements, and Cloudflare’s three-phase rollout (Phase 1 passthrough beta on April 30, 2026; Phase 2 edge-managed dictionaries; Phase 3 automatic dictionary generation), with lab results showing dramatic size and download-time reductions.