The design of USB aimed to remove the need for adding separate expansion cards into the computer's ISA or PCI bus, and improve plug-and-play capabilities by allowing devices to be hot swapped (or added to the system without rebooting the computer). When the new device first plugs in, the host enumerates it and loads the device driver necessary to run it.

USB can connect peripherals such as mice, keyboards, game pads and joysticks, scanners, digital cameras, printers, hard disks, and networking components. For multimedia devices such as scanners and digital cameras, USB has become the standard connection method. For printers, USB has also grown in popularity and started displacing parallel ports because USB makes it simple to add more than one printer to a computer. As of 2004 there were about 1 billion USB devices in the world. As of 2005, the only large classes of peripherals that cannot use USB (because they need a higher data rate than USB can provide) are displays and monitors, data acquisition devices that use FireWire ports, and high-quality digital video components