A dongle is a small device, typically about the size of a flash drive, that plugs in to a computer. Some dongles act as security keys while others serve as adapters. While early dongles connected to parallel ports on PCs and ADB ports on Macs, modern versions typically connect to a USB port.
Security dongles are used for copy protection are designed to prevent software piracy. For example, some high-end software applications, such as professional audio and video production programs, require a dongle in order to run. The dongle, which is included with the software, must be plugged in when you open the software program. If the correct dongle is not detected, the application will produce an error message saying a dongle is required in order to use the software.
Certain types of adapters are also called dongles. For instance, a dongle may provide a laptop with different types of wired connections. Previous generations of laptops had expansion slots called PCMCIA ports that were too skinny to include an Ethernet jack. Therefore, a dongle was required. These types of dongles were typically one to three inch cables that connected to the card on one end and had an Ethernet jack on the other. Modern Ethernet dongles have a similar appearance, but they usually connect to a USB or Thunderbolt port.
Today, many dongles provide wireless capabilities. For example, USB Wi-Fi adapters are often called dongles. Since most computers now have built-in Wi-Fi chips, cellular data adapters, such as 3G and 4G dongles, are more prevalent. These types of dongles allow you to connect to the Internet via a cellular carrier like Verizon or AT&T even when Wi-Fi is not available.