This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

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.


caches.keys().then(function(keyList) {
  //do something with your keyList


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




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 a whitelist containing the names of the caches we want to keep. We return the keys of the caches in the CacheStorage object using keys(), then check each key to see if it is in the whitelist. If not, we delete it using CacheStorage.delete.

then.addEventListener('activate', function(event) {
  var cacheWhitelist = ['v2'];

    caches.keys().then(function(keyList) {
      return Promise.all( {
        if (cacheWhitelist.indexOf(key) === -1) {
          return caches.delete(keyList[i]);


Specification Status Comment
Service Workers
The definition of 'CacheStorage' in that specification.
Working Draft Initial definition.

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari
Basic support 40.0 44 (44)[1] No support ? No support
Feature Android Android Webview Firefox Mobile (Gecko) IE Mobile Opera Mobile Safari Mobile Chrome for Android
Basic support No support No support 44.0 (44) (Yes) (Yes) (Yes) 40.0

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API CacheStorage Experimental Expérimental keys Method Reference Référence Service Workers ServiceWorker