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

<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

Browser compatibility

See also

• MouseEvent