Web/API/WindowEventHandlers/onunload

The onunload property of the WindowEventHandlers mixin is the EventHandler for processing unload events. These events fire when the window is unloading its content and resources. The resource removal is processed after the unload event occurs.

Note: Browsers equipped with pop-up blockers will ignore all Window.open() method calls in onunload event handler functions.

The onunload (and the unload event itself) are not the right features to use with sendBeacon(). Instead for sendBeacon(), use the visibilitychange and pagehide events. See discussion comments in the blog post Beacon API is broken.

Syntax

window.addEventListener("unload", function(event) { ... });
window.onunload = function(event) { ... };

Typically, it is better to use window.addEventListener() and the unload event, instead of onunload.

Specifications

Specification	Status	Comment
HTML Living StandardThe definition of 'onunload' in that specification.	Living Standard
HTML 5.1The definition of 'GlobalEventHandlers' in that specification.	Recommendation
HTML5The definition of 'GlobalEventHandlers' in that specification.	Recommendation

Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
onunload	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support  

Full support

In Firefox 1.5, using this event handler in your page prevents the browser from caching the page in the in-memory bfcache. See Using Firefox 1.5 caching for details.

WindowEventHandlers.onunload by Mozilla Contributors is licensed under CC-BY-SA 2.5.