No-Vary-Search is an HTTP response header that lets servers tell caches which query parameters are irrelevant for cache key matching. This solves the common problem where URLs with different UTM or tracking parameters — but identical content — are stored as separate cache entries. The header supports several modes: ignoring specific parameters, ignoring all parameters, ignoring all except a named set, and ignoring parameter order. It's particularly useful for marketing-heavy sites where analytics tags fragment the cache unnecessarily. As of mid-2026 it remains experimental, so it should be treated as progressive enhancement. A notable debugging gotcha: appending random query params to bust cache may no longer work on pages using this header.
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The Problem We’re SolvingWhat No-Vary-Search DoesA Simple ExampleNo-Vary-Search SyntaxesA Small Syntax GotchaA Small Debugging GotchaUse It CarefullyA Nice Fit for Messy Real-World URLsSort: