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

Note: This feature is only available in Service Workers.

The ExtendableCookieChangeEvent interface of the Cookie Store API is the event type passed to cookiechange event fired at the ServiceWorkerGlobalScope when any cookie changes occur which match the service worker's cookie change subscription list. 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.

Event ExtendableEvent ExtendableCookieChangeEvent



Creates a new ExtendableCookieChangeEvent.

Instance properties

This interface also inherits properties from ExtendableEvent.

ExtendableCookieChangeEvent.changed Read only

Returns an array containing the changed cookies.

ExtendableCookieChangeEvent.deleted Read only

Returns an array containing the deleted cookies.

Instance methods

This interface also inherits methods from ExtendableEvent.


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

Browser compatibility

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