USB products are classified by speed rather than just the specification number. Referring to a product as being compliant with a particular version of USB, while accurate, may not provide the information needed to be communicated.
The USB Implementers Forum has approved several specifications for USB which are all numbered. Most of the specifications have included a new signalling speed. USB specifications also state that speeds from previous version are to be included. For example USB 2.0 introduces High Speed USB, but also provides for Low and Full speed USB, first defined in USB 1.0, to be part of the specification. Stating that a product is "a USB 2.0 device" does not inform as to the actual transfer speeds implemented.
Commonly used USB Specifications
|USB 1.1||Low Speed
|USB 2.0||High Speed||480 Mbits/sec|
|USB 3.0||Super Speed||5 Gbits/sec|
|USB 3.1||Super Speed Plus||10 Gbits/sec|
Power Distribution and New Connector Specifications
|Type-C||New connector||5 V 3 A||Can work in conjunction with Power Delivery 2.0|
|Battery Charging 1.2||5 V 1.5 A|
|Power Delivery 2.0||Higher Power||100 W||Uses CC pin on Type-C connector for
|Host Supplied Power Options||5 V up to 0.9 A||USB 2.0 offers 500 mA, 3.0 offers 900 mA|