This feature is non-standard and is not on a standards track. Do not use it on production sites facing the Web: it will not work for every user. There may also be large incompatibilities between implementations and the behavior may change in the future.

Deprecated since Gecko 57 (Firefox 57 / Thunderbird 57 / SeaMonkey 2.54)
This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The non-standard, Firefox-only, TabClose event is sent by Firefox when a tab is closed.

Only Firefox itself and Firefox XPCOM-based add-ons can receive this event. XPCOM add-ons have been obsoleted by WebExtensions. If you're writing an add-on, please use tabs.onRemoved to detect when a tab is removed.

If you're writing code for the Web, you can't specifically determine when a tab is closed; however, you can detect when the current document closes by watching for an unload event.

General info

Specification Firefox add-ons specific
Interface Event
Bubbles Yes
Cancelable No
Target tab
Default Action None


Property Type Description
targetRead only EventTarget The event target (the topmost target in the DOM tree).
typeRead only DOMString The type of event.
bubblesRead only Boolean Whether the event normally bubbles or not.
cancelableRead only Boolean Whether the event is cancellable or not.

The target element can also be used as a DOM Window.


This example listens for the TabClose event and, when it occurs, looks in the closing tab for a <textarea> element with the ID "myEditor"; if it's found, the element's text is sent to a function called saveDocument() for processing.

window.addEventListener("TabClose", function(event) {
  var editor ="myEditor");

  if (editor) {
}, false);

See also

Document Tags and Contributors

Contributors to this page: chrisdavidmills, ExE-Boss, fscholz, Sheppy, teoli, ethertank, louisremi
Last updated by: ExE-Boss,