Based on its internal operation, a mouse can be classified as being:

- Mechanical: This mouse has a rubber ball that rotates as the mouse is moved on a flat surface. Two rollers attached to the ball, along the X and Y axes, translate the ball rotation into the rotation of two wheels. This wheels rotation alternately blocks and allows the passage of infrared lights. This causes blinking that is detected by two sensors and sent to the computer so as to be translated into a new X,Y position for the onscreen pointer.

- Optical: This mouse does not have any moving parts. It only works with a special pad that has gridlines printed on it. It has an internal light source and a sensor that is used to sense the number of vertical and horizontal pad gridlines passed by the light while moving the mouse. This information is sent to the computer so as to be translated into a new X,Y position for the onscreen pointer.