A dongle is a small hardware device that connects to a computer to authenticate a piece of software. 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. Vendors of software protection dongles (and dongle-controlled software) often use terms such as hardware key, hardware token, or security device in their written literature. In day-to-day use however, the jargon word "dongle" is much more commonly used.
The term has been somewhat generalized to describe specialized connectors that convert one type of port to another, for example an RJ45 jack that plugs into the edge connector on some kinds of PC card Ethernet adaptors, as well as small devices such as USB flash drives or wireless networking adapters. In addition, author Douglas Adams, in a 1990s column for the US edition of MacWorld magazine, used the term "little dongly things" to describe plug converters necessary for adapting US power cables to international plugs. These usages are not universally accepted.
Software protection dongles are typically used with very expensive packages (starting with about USD 500 and up) and vertical market software, such as CAD/CAM software, MICROS Systems hospitality and special retail software, Digital Audio Workstation applications and some translation memory packages. The vast majority of Printing and Prepress software, such as CtP work flows require dongles. Efforts to introduce dongle copy prevention in the mainstream software market were generally met with stiff resistance from users. Despite being hardware, dongles are not a complete solution to the trusted client problem.
Some times, in cases such as Prepress and Printing software, the dongle is encoded with a specific, per-user licence key, which determines which software features are enabled in the target application. This is a form of extremely restrictive licensing, which allows the vendor to engage in Vendor Lock-in and licence overpricing. An example of this practice is seen in the way Creo licences Prinergy to customers: When a Computer-to-plate output device is sold to a customer, Prinergy's own licence cost is provided separately to the customer, and the base price contains little more than the required licences to output work to the device. In order to access the advertised features in the application, the customer must pay a significant amount of money for a special dongle.
Well-known software protection dongle manufacturers include Matrix (Matrix Dongle) Matrix Software License Protection System, SafeNet (better known as Rainbow), Aladdin, WIBU-SYSTEMS,SG-Lock.,and Senselock (or Sense), and In the digital audio world, some versions of Pro Tools and many plugins use the Pace iLok Smart Key USB dongle.