index.md

---

title: cookies.OnChangedCause
slug: Mozilla/Add-ons/WebExtensions/API/cookies/OnChangedCause
page-type: webextension-api-type
tags:
  - API
  - Add-ons
  - Cookies
  - Extensions
  - Non-standard
  - OnChangedCause
  - Reference
  - Type
  - WebExtensions
browser-compat: webextensions.api.cookies.OnChangedCause

---

{{AddonSidebar()}}

The OnChangedCause type of the {{WebExtAPIRef("cookies")}} API represents the reason a cookie changed.

Type

Values of this type are strings. Possible values are:

• evicted

  • : A cookie has been automatically removed due to garbage collection.

• expired

  • : A cookie has been automatically removed due to expiry.

• explicit

  • : A cookie has been inserted or removed via an explicit call to {{WebExtAPIRef("cookies.remove()")}}.

• expired_overwrite

  • : A cookie has been overwritten by a cookie with an already-expired expiration date.

• overwrite

  • : A call to {{WebExtAPIRef("cookies.set()")}} overwrote this cookie with a different one.

Browser compatibility

{{Compat}}

Examples

You can listen to the {{WebExtAPIRef("cookies.onChanged")}} event to be notified when cookies change. The listener is passed a changeInfo object that contains a cause property, whose value is the OnChangeCaused string:

browser.cookies.onChanged.addListener((changeInfo) => {
  console.log(`Cookie changed: \n`
    + ` * Cookie: ${JSON.stringify(changeInfo.cookie)}\n`
    + ` * Cause: ${changeInfo.cause}\n`
    + ` * Removed: ${changeInfo.removed}`);
});

{{WebExtExamples}}

Note: This API is based on Chromium's chrome.cookies API. This documentation is derived from cookies.json in the Chromium code.