Product key

A product key, or software key, is a specific software-based key for a computer program. It certifies that the copy of the program is original.

Product keys consist of a series of numbers and letters. This sequence is typically entered by the user during the installation of computer software, and is then passed to a verification function in the program. This function manipulates the key sequence according to a mathematical algorithm and attempts to match the results to a set of valid solutions.

Microsoft products such as the Office productivity suite and Windows operating system require a 25-character product key that helps verify that the product has not been used on more devices than the Microsoft Software License Terms allow.