a dongle is a small hardware device that connects to a computer to authenticate some piece of software. this was its primary meaning in the computer industry in the 1980s and 1990s. when the dongle is not present, the software runs in a restricted mode or refuses to run. dongles are used by some proprietary vendors as a form of copy prevention or digital rights management because it is much harder to copy the dongle than to copy the software it authenticates.