The MouseEvent.buttons read-only property indicates which buttons are pressed on the mouse when the event is triggered.

Each button that can be pressed is represented by a given number (see below). If more than one button is pressed, the value of the buttons is combined to produce a new number. For example, if the right button (2) and the wheel button (4) are pressed, the value is equal to 2|4, which is 6.

Note: Do not confuse this property with the MouseEvent.button property. The MouseEvent.buttons property indicates the state of buttons pressed during any kind of mouse event, while the MouseEvent.button property only guarantees the correct value for mouse events caused by pressing or releasing one or multiple buttons.


var buttonPressed = instanceOfMouseEvent.buttons

Return value

A number representing one or more buttons. For more than one button pressed, the values are combined.

  • : No button or un-initialized
  • : Left button
  • : Right button
  • : Wheel button or middle button
  • : 4th button (typically the "Browser Back" button)
  • 16 : 5th button (typically the "Browser Forward" button)


Specification Status Comment
Document Object Model (DOM) Level 3 Events Specification
The definition of 'MouseEvent.buttons' in that specification.
Working Draft Initial definition

Browser compatibility

Feature Firefox (Gecko) Chrome Internet Explorer Opera Safari
Basic support (Yes)[1] 43[2] 9 (Yes) No support
Feature Firefox Mobile (Gecko) Android IE Mobile Opera Mobile Safari Mobile
Basic support ? ? ? ? ?

[1] Gecko supports the buttons attribute on Windows, Linux (GTK), and Mac OS with the following restrictions:

  • On Windows, if you install a mouse driver, and its utility software allows you to customize button actions (e.g., IntelliPoint and SetPoint), the middle (wheel) button, the 4th button, and the 5th button might not be set, even when they are pressed.
  • On Linux (GTK), the 4th button and the 5th button are not supported. In addition, a mouseup event always has the releasing button information in this attribute value.
  • On Mac OS X 10.5, the buttons attribute always returns 0 because there is no platform API for implementing this feature.

[2] This feature got implemented in bug 276941.

See also


© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.

API DOM DOM Events Property Read-only Reference UIEvent