The MouseEvent.button read-only property indicates which button was pressed on the mouse to trigger the event.

Users may change the configuration of buttons on their pointing device so that if an event's button property is zero, it may not have been caused by the button that is physically left–most on the pointing device; however, it should behave as if the left button was clicked in the standard button layout.

Note: Do not confuse this property with the MouseEvent.buttons property.


var buttonPressed = instanceOfMouseEvent.button

Return value

A number representing a given button:

  • -1: No button pressed
  • 0: Main button pressed, usually the left button
  • 1: Auxiliary button pressed, usually the wheel button or themiddle button (if present)
  • 2: Secondary button pressed, usually the right button
  • 3: Fourth button, typically the Browser Back button
  • 4: Fifth button, typically the Browser Forward button

For a mouse configured for left-handed use, the button actions are reversed. In this case, the values are read from right to left.


var whichButton = function (e) {
    // Handle different event models
    var e = e || window.event;
    var btnCode;

    if ('object' === typeof e) {
        btnCode = e.button;

        switch (btnCode) {
            case 0:
                console.log('Left button clicked.');

            case 1:
                console.log('Middle button clicked.');

            case 2:
                console.log('Right button clicked.');

                console.log('Unexpected code: ' + btnCode);

<button onmouseup="whichButton(event);" oncontextmenu="event.preventDefault();">Click with mouse...</button>


Specification Status Comment
Document Object Model (DOM) Level 3 Events Specification
The definition of 'MouseEvent.button' in that specification.
Working Draft Compared to Document Object Model (DOM) Level 2 Events Specification, the return value can be negative.
Document Object Model (DOM) Level 2 Events Specification
The definition of 'MouseEvent.button' in that specification.
Recommendation Initial definition.

Browser compatibility

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
Basic support 1.0 (1.7 or earlier) 1.0 9.0 [1] (Yes) 423
Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ? ?

[1] This convention is not followed in Internet Explorer prior to version 9: see QuirksMode for details.

See also

Document Tags and Contributors

Contributors to this page: Sebastianz, teoli, cvrebert, zastrowm, amycb, Jeremie
Last updated by: Sebastianz,