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. Developers can use No-Vary-Search to specify query parameters that have no impact on the user experience. A common example might be an id used to track conversions. Supporting this header in the HTTP disk cache means that if the user later goes back to that same page without the conversion id, it can be used or revalidated from the cache rather than having to be fetched from scratch from the network. Previously, No-Vary-Search support shipped for the navigation prefetch cache, prefetch and prerender speculation rules, and prerender. This launch makes it generally available to any feature that uses the HTTP disk cache.
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. It is possible to do this using the ServiceWorker API to build your own cache, however it is complex and comes with significant overhead. By supporting the No-Vary-Search response header, we can do the same thing easily with minimal overhead.
Docs: https://docs.google.com/document/d/1RS3q6qZ7-k9CvZsDYseGOXzcdQ9fGZ6YYnaW7fTPu7A/edit
Explainers: https://github.com/WICG/nav-speculation/blob/main/no-vary-search.md