CacheStorage: keys() method

Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

Note: This feature is available in Web Workers.

The keys() method of the CacheStorage interface returns a Promise that will resolve with an array containing strings corresponding to all of the named Cache objects tracked by the CacheStorage object in the order they were created. Use this method to iterate over a list of all Cache objects.

You can access CacheStorage through the Window.caches property in windows or through the WorkerGlobalScope.caches property in workers.

Syntax

js
keys()

Parameters

None.

Return value

a Promise that resolves with an array of the Cache names inside the CacheStorage object.

Examples

In this code snippet we wait for an activate event, and then run a waitUntil() block that clears up any old, unused caches before a new service worker is activated. Here we have an allowlist containing the names of the caches we want to keep (cacheAllowlist). We return the keys of the caches in the CacheStorage object using keys(), then check each key to see if it is in the allowlist. If not, we delete it using CacheStorage.delete().

js
this.addEventListener("activate", (event) => {
  const cacheAllowlist = ["v2"];

  event.waitUntil(
    caches.keys().then((keyList) =>
      Promise.all(
        keyList.map((key) => {
          if (!cacheAllowlist.includes(key)) {
            return caches.delete(key);
          }
        }),
      ),
    ),
  );
});

Specifications

Specification
Service Workers
# cache-storage-keys

Browser compatibility

BCD tables only load in the browser

See also