Cloudflare Adds Support for the Vary HTTP Header

Cloudflare has announced the implementation of support for the 'Vary' HTTP header, a feature often described as one of the most complex and misunderstood components of the HTTP protocol. The Vary header allows origin servers to inform caches that a response depends on specific request headers, such as 'Accept-Encoding' or 'User-Agent'. By correctly handling Vary, Cloudflare aims to improve cache hit ratios and ensure that users receive the most appropriate version of cached content. This update addresses long-standing developer feedback regarding the difficulty of managing cache variations across edge networks. The implementation includes robust logic to handle header normalization and cache key generation, significantly simplifying how developers manage dynamic content delivery. This enhancement is part of Cloudflare's ongoing effort to optimize edge performance and provide more granular control over how content is cached and served to global users.