Web/API/MouseEvent/altKey

The MouseEvent.altKey read-only property is a Boolean that indicates whether the alt key was pressed or not when a given mouse event occurs.

Be aware that the browser can't always detect the alt key on some operating systems. On some Linux variants, for example, a left mouse click combined with the alt key is used to move or resize windows.

Note: On Macintosh keyboards, this key is also known as the option key.

Syntax

var altKeyPressed = instanceOfMouseEvent.altKey

Return value

A Boolean, where true indicates that the key is pressed, and false indicates that the key is not pressed.

Example

This example logs the altKey property when you trigger a click event.

HTML

<p>Click anywhere to test the <code>altKey</code> property.</p>
<p id="log"></p>

JavaScript

let log = document.querySelector('#log');
document.addEventListener('click', logKey);

function logKey(e) {
  log.textContent = `The alt key is pressed: ${e.altKey}`;
}

Result

Specifications

Specification	Status	Comment
Document Object Model (DOM) Level 3 Events SpecificationThe definition of 'MouseEvent.altkey' in that specification.	Obsolete	No change from Document Object Model (DOM) Level 2 Events Specification.
Document Object Model (DOM) Level 2 Events SpecificationThe definition of 'MouseEvent.altkey' in that specification.	Obsolete	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`altKey`	Chrome Full support Yes	Edge Full support 12	Firefox Full support Yes	IE Full support Yes	Opera Full support Yes	Safari Full support Yes	WebView Android Full support Yes	Chrome Android Full support Yes	Firefox Android Full support Yes	Opera Android Full support Yes	Safari iOS Full support Yes	Samsung Internet Android Full support Yes

Legend

Full support: Full support