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---
title: ServiceWorkerGlobalScope
slug: Web/API/ServiceWorkerGlobalScope
tags:
- API
- Interface
- NeedsTranslation
- Offline
- Reference
- Service Workers
- ServiceWorkerGlobalScope
- TopicStub
translation_of: Web/API/ServiceWorkerGlobalScope
---
{{APIRef("Service Workers API")}}
The **`ServiceWorkerGlobalScope`** interface of the [Service Worker API](/en-US/docs/Web/API/Service_Worker_API) represents the global execution context of a service worker.
Developers should keep in mind that the ServiceWorker state is not persisted across the termination/restart cycle, so each event handler should assume it's being invoked with a bare, default global state.
Once successfully registered, a service worker can and will be terminated when idle to conserve memory and processor power. An active service worker is automatically restarted to respond to events, such as {{domxref("ServiceWorkerGlobalScope.onfetch")}} or {{domxref("ServiceWorkerGlobalScope.onmessage")}}.
Additionally, synchronous requests are not allowed from within a service worker — only asynchronous requests, like those initiated via the {{domxref("GlobalFetch.fetch", "fetch()")}} method, can be used.
This interface inherits from the {{domxref("WorkerGlobalScope")}} interface, and its parent {{domxref("EventTarget")}}, and therefore implements properties from {{domxref("WindowTimers")}}, {{domxref("WindowBase64")}}, and {{domxref("WindowEventHandlers")}}.
{{InheritanceDiagram(700, 85, 20)}}
## Properties
- {{domxref("ServiceWorkerGlobalScope.caches")}} {{readonlyinline}}
- : Contains the {{domxref("CacheStorage")}} object associated with the service worker.
- {{domxref("ServiceWorkerGlobalScope.clients")}} {{readonlyinline}}
- : Contains the {{domxref("Clients")}} object associated with the service worker.
- {{domxref("ServiceWorkerGlobalScope.registration")}} {{readonlyinline}}
- : Contains the {{domxref("ServiceWorkerRegistration")}} object that represents the service worker's registration.
## Events
- {{domxref("ServiceWorkerGlobalScope/activate_event", "activate")}}
- : Occurs when a {{domxref("ServiceWorkerRegistration")}} acquires a new {{domxref("ServiceWorkerRegistration.active")}} worker.
Also available via the {{domxref("ServiceWorkerGlobalScope.onactivate")}} property.
- {{domxref("ServiceWorkerGlobalScope/contentdelete_event", "contentdelete")}}
- : Occurs when an item is removed from the {{domxref("ContentIndex", "Content Index")}}.
Also available via the {{domxref("ServiceWorkerGlobalScope.oncontentdelete")}} property.
- `fetch`
- : Occurs when a {{domxref("GlobalFetch.fetch", "fetch()")}} is called.
Also available via the {{domxref("ServiceWorkerGlobalScope.onfetch")}} property.
- {{domxref("ServiceWorkerGlobalScope/install_event", "install")}}
- : Occurs when a {{domxref("ServiceWorkerRegistration")}} acquires a new {{domxref("ServiceWorkerRegistration.installing")}} worker.
Also available via the {{domxref("ServiceWorkerGlobalScope.oninstall")}} property.
- {{domxref("ServiceWorkerGlobalScope/message_event", "message")}}
- : Occurs when incoming messages are received. Controlled pages can use the {{domxref("MessagePort.postMessage()")}} method to send messages to service workers. The service worker can optionally send a response back via the {{domxref("MessagePort")}} exposed in [`event.data.port`](https://html.spec.whatwg.org/multipage/comms.html#messageport), corresponding to the controlled page.
Also available via the {{domxref("ServiceWorkerGlobalScope.onmessage")}} property.
- {{domxref("ServiceWorkerGlobalScope/notificationclick_event", "notificationclick")}}
- : Occurs when a user clicks on a displayed notification.
Also available via the {{domxref("ServiceWorkerGlobalScope.onnotificationclick")}} property.
- `notificationclose`
- : Occurs — when a user closes a displayed notification.
Also available via the {{domxref("ServiceWorkerGlobalScope.onnotificationclose")}} property.
- {{domxref("ServiceWorkerGlobalScope/push_event", "push")}}
- : Occurs when a server push notification is received.
Also available via the {{domxref("ServiceWorkerGlobalScope.onpush")}} property.
- {{domxref("ServiceWorkerGlobalScope/pushsubscriptionchange_event", "pushsubscriptionchange")}}
- : Occurs when a push subscription has been invalidated, or is about to be invalidated (e.g. when a push service sets an expiration time).
Also available via the {{domxref("ServiceWorkerGlobalScope.onpushsubscriptionchange")}} property.
- `sync`
- : Triggered when a call to {{domxref("SyncManager.register")}} is made from a service worker client page. The attempt to sync is made either immediately if the network is available or as soon as the network becomes available.
Also available via the {{domxref("ServiceWorkerGlobalScope.onsync")}} property.
## Methods
- {{domxref("ServiceWorkerGlobalScope.skipWaiting()")}}
- : Allows the current service worker registration to progress from waiting to active state while service worker clients are using it.
`ServiceWorkerGlobalScope` implements {{domxref("WorkerGlobalScope")}} — which implements {{domxref("WindowOrWorkerGlobalScope")}}. Therefore it also has the following property available to it:
- {{domxref("GlobalFetch.fetch()")}}
- : Starts the process of fetching a resource. This returns a promise that resolves to the {{domxref("Response")}} object representing the response to your request. This algorithm is the entry point for the fetch handling handed to the service worker context.
## Examples
This code snippet is from the [service worker prefetch sample](https://github.com/GoogleChrome/samples/blob/gh-pages/service-worker/prefetch/service-worker.js) (see [prefetch example live](https://googlechrome.github.io/samples/service-worker/prefetch/).) The {{domxref("ServiceWorkerGlobalScope.onfetch")}} event handler listens for the `fetch` event. When fired, the code returns a promise that resolves to the first matching request in the {{domxref("Cache")}} object. If no match is found, the code fetches a response from the network.
The code also handles exceptions thrown from the {{domxref("GlobalFetch.fetch", "fetch()")}} operation. Note that an HTTP error response (e.g., 404) will not trigger an exception. It will return a normal response object that has the appropriate error code set.
```js
self.addEventListener('fetch', function(event) {
console.log('Handling fetch event for', event.request.url);
event.respondWith(
caches.match(event.request).then(function(response) {
if (response) {
console.log('Found response in cache:', response);
return response;
}
console.log('No response found in cache. About to fetch from network...');
return fetch(event.request).then(function(response) {
console.log('Response from network is:', response);
return response;
}, function(error) {
console.error('Fetching failed:', error);
throw error;
});
})
);
});
```
## Specifications
| Specification | Status | Comment |
| ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------ | ------------------ |
| {{SpecName('Service Workers', '#serviceworkerglobalscope-interface', 'ServiceWorkerGlobalScope')}} | {{Spec2('Service Workers')}} | Initial definition |
## Browser compatibility
{{Compat("api.ServiceWorkerGlobalScope")}}
## See also
- [Using Service Workers](/en-US/docs/Web/API/ServiceWorker_API/Using_Service_Workers)
- [Service workers basic code example](https://github.com/mdn/sw-test)
- [Is ServiceWorker ready?](https://jakearchibald.github.io/isserviceworkerready/)
- {{jsxref("Promise")}}
|
