Compression Dictionary Transport becomes RFC 9842, enabling delta bundle downloads

Compression Dictionary Transport was standardized as RFC 9842 in September 2025 and ships in Chrome and Edge 130+. It compresses a new file version against a cached one, cutting a 272 KB JavaScript bundle to 2.6 KB in Cloudflare's lab test.

• RFC 9842 was published in September 2025, supported in Chrome and Edge 130+
• In Cloudflare's test a 272 KB bundle shrank to 2.6 KB versus 92.2 KB with gzip
• Servers mark files with Use-As-Dictionary; browsers send the hash in Available-Dictionary
• Firefox has an active implementation, Safari has not announced support; fallback is normal Brotli