beforeunload

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.

Baseline Status: This feature is currently Limited and is missing in at least one major browser engine.

Desktop Browser Engine Support

Google Chrome

1

Supported

Mozilla Firefox

1

Supported

Apple Safari

3

Supported

Microsoft Edge

12

Supported

Mobile Browser Engine Support

Chrome Android

18

Firefox Android

4

Safari iOS

—

Specifications and References

Specification ↗ Feature XML ↗

MDN Browser Compat Data Keys:

api.BeforeUnloadEvent ↗ api.BeforeUnloadEvent.user_interaction ↗ api.Window.beforeunload_event ↗ api.Window.beforeunload_event.preventdefault_activation ↗