Scroll wheel

A scroll wheel is a wheel on a computer mouse. It is used, as the name suggests, for scrolling. It can also be used as a third mouse button by pressing on it. Some newer mice even have scroll wheels with can be tilted from side-to-side for horizontal scrolling controls. In most programs, holding down the control key and using the scroll wheel causes the text size to increase or decrease.

The scroll wheel first gained popularity in the late nineties, and is notable in that it was one of the first additions to the basic two-button mouse design used on PCs that really stuck. It is also probably one of the first hardware elements (aside from high-speed modems) designed directly in response to the proliferation of the World Wide Web (where efficient mouse-only scrolling is most useful).

Scroll wheels are quite prevalent on modern computer mice. To many users, they have become an integral part of the hardware interface. Non-wheeled mice are still available, however. Notably, Apple Computers come with a non-wheeled mouse by default.

Scroll wheels can also be found on such handheld devices as portable Digital audio players, Pocket PCs or BlackBerry devices.