What is sensitivity? A common misunderstanding is that mouse sensitivity adjusts the speed of the input from the mouse, or the speed of your crosshair/character movement. While increased or decreased movement speed is the primarily perceived effect, what it really does is modifying how far each count from the mouse moves your crosshair.   When you are adjusting the sensitivity, you are actually defining a grid to which your movement snaps. The lower the sensitivity, the finer the grid.