v141 · network / connectivity

No-Vary-Search support for the HTTP disk cache

Enables the HTTP disk cache to use the No-Vary-Search response header to share a cache entry between URLs that differ only in the query parameters.

concepts

  1. NVS in disk cache

    No-Vary-Search rules now apply to the HTTP disk cache, not just memory. Long-tail tracking parameters no longer fragment the cache across sessions.

  2. UTM Collapse

    Hit the same hero with four utm/fbclid combinations. Watch the bytes column collapse from 4× to 1× as the disk cache treats them as the same entry.

  3. key-order & except

    The three directives the spec defines — params, except, key-order — interact in non-obvious ways. Build a header, enter two URLs, see whether they'd hit the same cache key.

  4. Cache Key Tester

    Type a No-Vary-Search header value and two URLs, get an instant same-or-different cache-key verdict with an explanation of which params were ignored or normalised. A preset gallery covers the five most common UTM/analytics patterns.

why it shipped

It's common for URLs to have query parameters that contain information that is important for technical or business reasons but doesn't change the user experience. When the same resource is fetched a second time with a different value for these parameters, it is often desirable to serve it from the HTTP disk cache rather than downloading it from the origin server again. This can improve responsiveness for the user, and save bandwidth for both the user and developer.

references