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 Specification
The 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 Specification
The definition of 'MouseEvent.altkey' in that specification.
Obsolete Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
altKeyChrome Full support YesEdge Full support 12Firefox Full support YesIE Full support YesOpera Full support YesSafari Full support YesWebView Android Full support YesChrome Android Full support YesFirefox Android Full support YesOpera Android Full support YesSafari iOS Full support YesSamsung Internet Android Full support Yes

Legend

Full support  
Full support

See also