A dongle is a small device that connects with another device to provide additional functionality.
The term dongle is predominately used to describe hardware providing a copy protection mechanism for commercial software. The hardware device must be attached to a computer or device in order to unlock software functionality or decode content.
As a software protection device, dongles appear as two-interface security tokens with transient data flow. The software will not run, or alternatively run in a restricted mode, if the dongle is not attached to the computer or device.
Commonly the term dongle is also used to refer to devices which provide wifi to devices via a USB connection, as well as digital media players such as Amazon Fire TV, Chromecast and Roku.