Also known as a receptacle or female connector, the socket provides the port into which the plug pins are inserted. Most socket types are circular or rectangular, but they come in a wide array of sizes and shapes. They usually provide more of the structural rigidity and support when the housing the plug, since sockets are housing the delicate pins. For this reason, they are usually larger and heavier.

The socket is typically responsible for electrical isolation, proper connector orientation (keyed), good electrical contact between pins and receptacles, and possibly the mechanical locking of the connection. Because of the hundreds of varieties of connectors and thousands of possible applications, the usefulness and criticality of these responsibilities can vary widely. Some high voltage applications require a wider spacing of the pin receptacles, and higher current requires larger receptacles. In hardier environments often a threaded lock socket is utilized to ensure the connection never comes undone, but in many stationary computer applications there is only a friction lock, meaning the tightness between the socket and the plug.