By default, most computer users use the left button of the mouse in order to open a file or to perform other tasks. I know is it up to a user to configure the left or right button as the main button, but why does it default to the left and why do companies like Apple offer single-button mice?

  • 3
    Because you press things using your index finger, and the left button is where your index finger sits.
    – JonW
    Commented Feb 24, 2017 at 12:43
  • @JonW but you also presses things using other fingers, not only by index or trigger finger.
    – Krebto
    Commented Feb 24, 2017 at 13:19
  • 1
    You primarily press with your index finger, and you also press with other fingers. The mouse button supports your primary behavior. Commented Feb 24, 2017 at 13:44

1 Answer 1


The left-click operation is normally operated by the index (pointing) finger, which is usually dominant (being the most dextrous and sensitive). The left button of a mouse is configured as the primary button by default because that suits the vast majority (~90%) of right-handed users.

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