A serial key or product code verifies that a user's copy of a software program comes from a legitimate purchase. Many paid-for programs typically ask for serial keys during installation and product activation. Developers use serial keys to protect products against copyright infringement and software piracy.
A serial key is synonymous to other terms, including CD key, installation key and product key. In general, it is an alphanumeric code that is unique for every copy of a software program. A user is responsible for keeping his product keys, which he may need again when reinstalling his programs. If he loses his key, the user can try using product key finders to search the computer and retrieve the lost key. Otherwise, buying a new copy of the program is the only legitimate way of regaining a software license.
Because of the prevalence of product key generators and cracking tools, software developers may employ additional methods to supplement product keys for product validation. One method is to use hardware information, such as the MAC address, to associate with the product keys. Another method is to require users to connect to an online server. Skipping product activation or failing to pass product validations may cause the software to run with reduced functionality.