beforeunload
Limited availability
The beforeunload event is fired when the current window is about to be unloaded. Typically this is used to display a dialog to confirm if users really want to leave the page when there is unsaved data that would be lost.
Learning resources on MDN
Browser support
- Chrome 1 Released on 2008-12-11
- Chrome Android 18 Released on 2012-06-27
- Edge 12 Released on 2015-07-29
- Firefox 1 Released on 2004-11-09
- Firefox for Android 4 Released on 2011-03-29
- Safari 3 Released on 2007-10-26
- Safari on iOS ❌ See webkit.org/b/219102
Baseline availability blocked since July 2015 by Safari on iOS (117 months)
Usage (according to Chrome Platform Status)
~56.192% of page loads. More data at chromestatus.
Specifications
- HTML (#the-beforeunloadevent-interface), from HTML Workstream (WHATWG).
View web-platform-tests results for this feature - View the feature source file (dist) - Edit the feature - Report an issue about this feature