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

The ExtendableCookieChangeEvent interface of the Cookie Store API is the event type passed to ServiceWorkerRegistration.oncookiechange() when any cookie changes have occurred. A cookie change event consists of a cookie and a type (either "changed" or "deleted".)

Cookie changes that cause the ExtendableCookieChangeEvent to be dispatched are:

  • A cookie is newly created and not immediately removed. In this case type is "changed".
  • A cookie is newly created and immediately removed. In this case type is "deleted"
  • A cookie is removed. In this case type is "deleted".

Note: A cookie that is replaced due to the insertion of another cookie with the same name, domain, and path, is ignored and does not trigger a change event.



Creates a new ExtendableCookieChangeEvent.


This interface also inherits properties from ExtendableEvent.

ExtendableCookieChangeEvent.changedRead only

Returns an array containing the changed cookies.

ExtendableCookieChangeEvent.deletedRead only

Returns an array containing the deleted cookies.


In the below example we use CookieStoreManager.getSubscriptions() to get a list of existing subscriptions. (In service workers, a subscription is required in order to listen for events.) We unsubscribe from existing subscriptions using CookieStoreManager.unsubscribe(), then subscribe to the cookie with a name of 'COOKIE_NAME' using CookieStoreManager.subscribe(). If that cookie is changed, the event listener logs the event to the console. This will be an ExtendableCookieChangeEvent object, with the changed or deleted property containing the modified cookie.

self.addEventListener('activate', (event) => {
  event.waitUntil(async () => {
    const subscriptions = await self.registration.cookies.getSubscriptions();
    await self.registration.cookies.unsubscribe(subscriptions);

    await self.registration.cookies.subscribe([
        name: 'COOKIE_NAME',

self.addEventListener('cookiechange', event => {


Cookie Store API
# ExtendableCookieChangeEvent

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