USB Protocols

The protocols in current use are USB 2.0, 3.0, and 3.1. Earlier versions are obsolete. Each version is fully compatible with earlier versions; a USB 3.1 hub can communicate with a 2.0 device, though it will be limited to 2.0 data rates. Each protocol supports more than one speed, including all the ones earlier versions support. The maximum speeds are:

  • USB 2.0: 480 Mbps
  • USB 3.0: 5 Gbps
  • USB 3.1: 5 Gbps or 10 Gbps

What is called USB 3.1 Gen 1 is effectively the same as 3.0. It delivers a top speed of 5 Gbps, called SuperSpeed or SS. USB 3.1 Gen 2 delivers 10 Gbps, called SuperSpeed+.

Compatibility runs in both directions. You can use a USB 3.1 drive with a computer that supports only 2.0, or the other way around. Of course, you’ll only get USB 2.0 speeds in either case. You should get a hub which supports a protocol version at least as high as the computer you’ll use it with.