Cloudflare Adds Vary Header Support to Cache Rules

Cloudflare Implements Vary Header Support

Cloudflare has announced the addition of support for the HTTP Vary response header within its Cache Rules. This feature is now available on all plans, providing users with more granular control over how their content is cached when multiple representations exist for a single URL.

Understanding the Vary Header

The Vary header is a standard HTTP mechanism that instructs intermediary caches, such as Cloudflare's, which request fields might influence the response sent by the origin server. Websites utilize Vary to serve different versions of content, like varying languages, image formats, compression schemes, or regional content, from the same URL.

For example, if a browser requests a webpage and an API client requests data from the same URL, the Vary: Accept header tells the cache that the 'Accept' header value must be considered when choosing between the HTML and JSON responses. Without Vary, the cache might serve the wrong content to either client.

Enhanced Cache Control

With this new support, while the origin server still specifies which request headers may affect a response, Cloudflare users can now define how these Vary headers are processed. Options include normalizing known negotiation headers, passing exact values when small differences are critical, or bypassing the cache entirely if the variation is too unpredictable. This allows users to determine how much variation is meaningful for their caching strategy.