Overview

In general, there are four basic kinds or sizes related to the USB connectors and types of established connections:

• the older "standard" size, in its USB 1.1/2.0 and USB 3.0 variants (for example, on USB flash drives)
• the "mini" size (primarily for the B connector end, such as on many cameras)
• the "micro" size, in its USB 1.1/2.0 and USB 3.0 variants (for example, on most modern cellphones)
• the versatile "USB On-The-Go" scheme, in both mini and micro sizes.

Unlike other data cables (Ethernet, HDMI etc.), each end of a USB cable uses a different kind of connector; an A-type or a B-type. This kind of design was chosen to prevent electrical overloads and damaged equipment, as only the A-type socket provides power. There are cables with A-type connectors on both ends, but they should be used carefully.[4] Therefore in general, each of the different "sizes" requires four different connectors; USB cables have the A-type and B-type connectors, and the corresponding sockets are on the computer or electronic device. In common practice, the A-type connector is usually the full size, and the B-type side can vary as needed.

Counter-intuitively, the "micro" size is the most durable from the point of designed insertion lifetime, as the result of latching mechanism (parts providing gripping force) being moved into plugs on the cable side.

USB connections also come in four data transfer speeds: Low Speed, Full Speed, High Speed and SuperSpeed. High Speed is only supported by specifically designed USB 2.0 High Speed interfaces (that is, USB 2.0 controllers without the High Speed designation do not support it), as well as by USB 3.0 interfaces. SuperSpeed is supported only by USB 3.0 interfaces.