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

• Window: beforeunload event

Browser support

• Chrome 119 Released on 2023-10-31
• Chrome Android 119 Released on 2023-10-31
• Edge 119 Released on 2023-11-02
• Firefox 6 Released on 2011-08-16
• Firefox for Android 6 Released on 2011-08-16
• Safari 11 Released on 2017-09-19
• Safari on iOS ❌

Baseline availability blocked since November 2023 by Safari on iOS (13 months)

Edit this feature - Report an issue about this feature