A dongle is a small piece of hardware that connects to another device to provide it with additional functionality. In relation to computing, the term is primarily associated with hardware providing a copy protection mechanism for commercial software—in which the dongle must be attached to the system that the software is installed on in order for it to function. The term "dongle" is also associated with similar devices meant to provide additional forms of wireless connectivity to devices (such as Wi-Fi or Bluetooth support), often over USB connections, as well as small form factor digital media players (such as Amazon Fire TV Stick, Chromecast, and Roku Streaming Stick) and personal computers (such as Chromebit and Intel Compute Stick) meant to plug directly into an HDMI input.
A software protection dongle (commonly known as a dongle or key) is an electronic copy protection and content protection device which, when attached to a computer or other electronic appliance, unlocks software functionality or decodes content. The hardware key is programmed with a product key or other cryptographic protection mechanism; it attaches via electrical connector to an external bus of the computer or appliance.
When used as a software protection device, dongles mostly appear as two-interface security tokens with transient data flow that does not interfere with other dongle functions and a pull communication that reads security data from the dongle. Without the dongle, the software may run only in a restricted mode, or not at all. When used as a device attached to a computer or TV or gaming console, dongles can enable functions that would not be present without it. For example, a dongle attached to a TV may receive an encoded video stream, decode it in the dongle, and then present this audio and video information to the TV.