This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The has() method of the CacheStorage interface returns a Promise that resolves to true if a Cache object matches the cacheName.


caches.has(cacheName).then(function(boolean) {
  // true: your cache exists!


a Promise that resolves to true if the cache exists or false if not.


A DOMString representing the name of the Cache object you are looking for in the CacheStorage.


The following example first checks whether a cache called 'v1' exists. If so, we add a list of assets to it. If not (meaning the has() promise would reject) then we run some kind of cache set-up function.

caches.has('v1').then(function(hasCache) {
  if (!hasCache) {
  } else {'v1').then(function(cache) {
      return cache.addAll(myAssets);
}).catch(function() {
  // Handle exception here.


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

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support40 Yes441 No27 No
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support4040 Yes4427 Yes ?

1. Service workers (and Push) have been disabled in the Firefox 45 & 52 Extended Support Releases (ESR.)

See also

Document Tags and Contributors

Last updated by: ExE-Boss,