Compression Dictionary Transport

This is a collection of references and tools related to using dictionary-based compression on the web.

Specs

The main overview document and reference is the W3C Compression Dictionary Transport document. It also includes a set of examples showing the impact of using dictionary-based compression.

The HTTP protocol-level parts of the compression dictionary is being developed through the IETF. The current Internet Draft (pre-RFC) is here.

Tools

• Dictionary Generator - Generate a dictionary from a list of URLs and, optionally, test the effectiveness of dictionary compression on those pages.
• Delta Compression Tester - Test the effectiveness of compressing a new version of a resource using a previous version as a dictionary.

Documentation

• WICG Explainer
• IETF Internet Draft
• CDN support - Configuration details for various CDNs to allow compression dictionary encoding.
• performance.now() 2023 conference presentation (Dark version here.)

Browser Status

Compression Dictionary Transport is available in Chrome 119 or later as an origin trial while the Header values go through the standards process. You can register for the origin trial here.