A password cracker is an application programme that is used to identify an unknown or forgotten password to a computer or network resources. It can also be used to help a human cracker obtain unauthorised access to resources.

Password crackers use two primary methods to identify correct passwords: brute-force and dictionary searches. When a password cracker uses brute-force, it runs through combinations of characters within a predetermined length until it finds the combination accepted by the computer system. When conducting a dictionary search, a password cracker searches each word in the dictionary for the correct password. Password dictionaries exist for a variety of topics and combinations of topics, including politics, movies, and music groups.