HTML onunload Attribute
Definition and Usage
The onunload attribute fires once a page has unloaded (or the browser window has been closed).
onunload occurs when the user navigates away from the page (by clicking on a link, submitting a form, closing the browser window, etc.)
Note: If you reload a page, you will also trigger the onunload event (and the onload event).
The onunload attribute is part of the Event Attributes, and can be used on the following element:
Note: Due to different browser settings, this event may not always work as expected.