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MouseEvent: altKey property

The MouseEvent.altKey read-only property is a boolean value 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.

Value

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

Examples

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

HTML

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
UI Events # dom-mouseevent-altkey

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`altKey`	1	12	1.5	9	≤12.1	1	≤37	18	4	≤12.1	1	1.0