Cache Storage API
A web API (the global caches object) for programmatically storing request/response pairs — primarily used by service workers for offline support and network caching in PWAs. You control exactly what's cached and when it's served from cache vs the network.
Mechanic: you open a named cache (caches.open("v1")) and store Response objects against Request keys; a service worker can then, in its fetch handler, choose to respond from the cache, from the network, or a combination. It differs from the browser's regular HTTP cache: this one is fully programmable — YOU decide the caching strategy. Common strategies: cache-first (fast, for static resources), network-first (fresh, with cache as a fallback offline), stale-while-revalidate (serve cache immediately, update in the background). Use case: offline-working PWAs, faster loading, the "app shell" pattern. Versioning the cache names (cleaning up old ones in the activate phase) is central. Related to service worker lifecycle and origin private file system.