We just shipped support for the ugliest part of HTTP: Vary
Curated from Cloudflare Blog
Vary header handling remains one of the most frequently misconfigured aspects of HTTP caching. Many teams inadvertently bypass their edge cache entirely because they fail to account for subtle negotiation headers, leading to unnecessary origin load and increased latency. This post is valuable because it moves beyond theoretical RFC compliance to demonstrate practical application within a global CDN framework. It addresses the common operational friction where developers must choose between aggressive caching and correctness, often sacrificing one for the other. The distinction between normalizing known headers and passing exact values through is particularly relevant for teams dealing with complex client capabilities. For working practitioners, the concrete takeaway is to audit your existing cache rules immediately: if you are currently using broad wildcards for Vary headers, you are likely discarding cache hits that could be safely served, and switching to specific normalization strategies can yield immediate performance gains.
Vary support is now available in Cache Rules on every plan. You can normalize known negotiation headers, pass exact values through to the origin when those small differences matter, or bypass cache when the variation is too unpredictable.
— Cloudflare Blog