index.md

---

title: runtime.onSuspend
slug: Mozilla/Add-ons/WebExtensions/API/runtime/onSuspend
page-type: webextension-api-event
tags:
  - API
  - Add-ons
  - Event
  - Extensions
  - Non-standard
  - Reference
  - WebExtensions
  - onSuspend
  - runtime
browser-compat: webextensions.api.runtime.onSuspend

---

{{AddonSidebar()}}

Sent to the event page just before it is unloaded. This gives the extension an opportunity to do some cleanup. Note that since the page is unloading, any asynchronous operations started while handling this event are not guaranteed to complete.

Note: If something prevents the event page from being unloaded, the {{WebExtAPIRef("runtime.onSuspendCanceled")}} event will be sent and the page won't be unloaded.

Syntax

browser.runtime.onSuspend.addListener(listener)
browser.runtime.onSuspend.removeListener(listener)
browser.runtime.onSuspend.hasListener(listener)

Events have three functions:

• addListener(callback)

  • : Adds a listener to this event.

• removeListener(listener)

  • : Stop listening to this event. The listener argument is the listener to remove.

• hasListener(listener)

  • : Checks whether a listener is registered for this event. Returns true if it is listening, false otherwise.

addListener syntax

Parameters

• callback

  • : Function that will be called when this event occurs.

Browser compatibility

{{Compat}}

Examples

Listen for suspend events:

function handleSuspend() {
  console.log("Suspending event page");
  // handle cleanup
}

browser.runtime.onSuspend.addListener(handleSuspend);

{{WebExtExamples}}

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