What is a USB Port?

USB-B Port - Standard Computer USB Port (close-up)
USB-B Port - Standard Computer USB Port (close-up). Don Farrall / Getty Images

A USB port is a standard cable connection interface for personal computers and consumer electronics devices. USB stands for Universal Serial Bus, an industry standard for short-distance digital data communications. USB ports allow USB devices to be connected to each other with and transfer digital data over USB cables. They can also supply electric power across the cable to devices that need it.

Both wired and wireless versions of the USB standard exist, although only the wired version involves USB ports and cables.

What Can You Plug Into a USB Port?

Many types of consumer electronics support USB interfaces. These types of equipment are most commonly used for computer networking:

For computer-to-computer file transfers without a network, USB drives are also sometimes used to copy files between devices.

Using a USB Port

Connect two devices directly with one USB cable by plugging each end into a USB port. (Some devices feature more than one USB port, but do not plug both ends of a cable into the same device, as this can cause electrical damage!)

​You may plug cables into a USB port at any time regardless of whether the devices involved are powered on or off. Follow instructions provided with your equipment before unplugging USB cables. In some cases, unplugging a USB cable from a running device can cause  

Multiple USB devices can also be connected to each other using a USB hub. A USB hub plugs into one USB port and contains additional ports for other devices to connect subsequently. If using a USB hub, plug a separate cable into each device and connect them to the hub individually. 

USB-A, USB-B and USB-C Port Types

Several major types of physical layouts exist for USB ports:

  • USB-B (Type B): This rectangular connector approximately 1.4 cm (9/16 in) length by 0.65 cm (1/4 in) height is commonly found on routers, computers, printers and game consoles. USB sticks normally feature USB-B connectors also.
  • USB-A (Type A): Less common than type B, USB A devices are nearly square in shape and are typically used for wired mice and keyboards.
  • Micro USB: So-called Micro USB versions of both USB-A and USB-B also exist - smaller versions than their base counterparts, popular on mobile devices. (Older but now obsolete "mini USB" versions can also be found on some old devices.)
  • USB Type C: With dimensions of 0.84 cm by 0.26cm, this newer standard is designed to replace both A and B with smaller ports to better support the thinner form factors of mobile devices

To connect a device having one kind of port a device with another type, simply use the correct type of cable with appropriate interfaces on each end. USB cables are manufactured to support all supported combinations of types and male/female options.

Versions of USB

USB devices and cables support multiple versions of the USB standard from version 1.1 up to the current version 3.1. USB ports feature identical physical layouts no matter the version of USB supported.

Alternatives to USB

USB ports are an alternative to the serial and parallel ports available on older PCs. USB ports support much faster (often 100x or greater) data transfers than serial or parallel.

For computer networking, Ethernet ports are sometimes used instead of USB. For some types of computer peripherals, FIreWire ports are also sometimes available. Both Ethernet and FireWire can offer faster performance than USB, although these interfaces do not supply any power across the wire.

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