# onbeforeunload Event

Event Object

## Example

Execute a JavaScript when the page is about to be unloaded:

<body onbeforeunload="return myFunction()">
Try it yourself »

## Definition and Usage

The onbeforeunload event occurs when the document is about to be unloaded.

This event allows you to display a message in a confirmation dialog box to inform the user whether he/she wants to stay or leave the current page.

The default message that appears in the confirmation box, is different in different browsers. However, the standard message is something like "Are you sure you want to leave this page?". This message cannot be removed.

However, you can write a custom message together with the default message. See the first example on this page.

Note: If the onbeforeunload event is not assigned to the <body> element, you must assign/attach the event on the window object, and use the returnValue property to create a custom message (see syntax examples below).

Note: In Firefox, only the default message will be displayed (not the custom message (if any)).

## Browser Support

The numbers in the table specify the first browser version that fully supports the event.

Event |  |  |  |  |
--- | --- | --- | --- | --- | ---
onbeforeunload | Yes | Yes | Yes | Yes | 15.0

## Syntax

In HTML:

<element onbeforeunload="myScript">Try it

In JavaScript:

object.onbeforeunload=function(){myScript};Try it

In JavaScript, using the addEventListener() method:

object.addEventListener("beforeunload", myScript);Try it

Note: The addEventListener() method is not supported in Internet Explorer 8 and earlier versions.

## Technical Details

Bubbles: | No
Cancelable: | Yes
Event type: | Event
Supported HTML tags: | <body>
DOM Version: | Level 2 Events

Event Object

### WEB HOSTING

UK Reseller Hosting

### WEB BUILDING

FREE Website BUILDER Free HTML5 Templates

### W3SCHOOLS EXAMS

HTML, CSS, JavaScript, PHP, jQuery, XML, and ASP Certifications

### SHARE THIS PAGE

### Color Picker

### HTML/CSS

HTML Tutorial HTML5 Tutorial CSS Tutorial CSS3 Tutorial Bootstrap Tutorial

### JavaScript

JavaScript Tutorial jQuery Tutorial jQuery Mobile Tutorial AngularJS Tutorial AJAX Tutorial JSON Tutorial

### Graphics

Canvas Tutorial SVG Tutorial Google Maps Tutorial

### Server Side

SQL Tutorial PHP Tutorial ASP Tutorial ASP.NET Tutorial VBScript Tutorial AppML Tutorial

### Web

Web Building Web Statistics Web Certification

### XML

XML Tutorial DTD Tutorial Schema Tutorial XML DOM Tutorial XPath Tutorial XSLT Tutorial XQuery Tutorial XSL-FO Tutorial RSS Tutorial WSDL Tutorial

### HTML/CSS

HTML Tag Reference HTML Event Reference HTML Color Reference CSS 1,2,3 Reference Bootstrap Reference

### JavaScript

JavaScript Reference HTML DOM Reference jQuery Reference jQuery Mobile Reference Google Maps Reference

### Server Side

PHP Reference SQL Reference ASP Reference VBScript Reference Razor Reference ASP.NET Reference

### XML

XML DOM Reference XSLT Reference XSL-FO Reference XPath Reference XQuery Reference Schema Reference RSS Reference SVG Reference

### HTML Charsets

HTML Character Sets HTML ASCII HTML ANSI HTML Windows-1252 HTML ISO-8859-1 HTML Symbols HTML UTF-8

### HTML/CSS

HTML Examples CSS Examples

### Browser Scripting

JavaScript Examples HTML DOM Examples jQuery Examples jQuery Mobile Examples AngularJS Examples AJAX Examples

### Server Scripting

PHP Examples ASP Examples VBScript Examples Razor Examples .NET Examples

### XML Languages

XML Examples DTD Examples XML DOM Examples XSL Examples XSLT Examples XPath Examples XQuery Examples Schema Examples RSS Examples SVG Examples