A computer fan is any fan inside, or attached to, a computer case used for active cooling, and may refer to fans that draw cooler air into the case from the outside, expel warm air from inside, or move air across a heat sink to cool a particular component. Alternatively referred to as a system fan, a case fan is located inside a computer, attached to the front or back of its case. Case Fans help bring cool air into and blow hot air out of the case.

The size of fan you need will generally be determined by the size of the fan fitting position in your PC case.