USB4

USB4

Type	USB
Production history
Designer	USB Promoter Group
Designed	29 August 2019; 5 years ago (2019-08-29)
Superseded	USB 3.2
General specifications
Daisy chain	No
Audio signal	DisplayPort
Video signal	DisplayPort
Pins	24
Connector	USB-C
Electrical
Max. voltage	48 V (PD 3.1)
Max. current	5 A (PD)
Data
Data signal	USB or PCIe
Bitrate	20 Gbit/s 40 Gbit/s 80 Gbit/s 120/40 Gbit/s asymmetric

Universal Serial Bus 4 (USB4), sometimes erroneously referred to as USB 4.0, is the most recent technical specification of the USB (Universal Serial Bus) data communication standard. The USB Implementers Forum originally announced USB4 in 2019.

USB4 enables multiple devices to dynamically share a single high-speed data link. USB4 defines bit rates of 20 Gbit/s, 40 Gbit/s and 80 Gbit/s.^[1][2] USB4 is only defined for USB-C connectors and its Type-C specification^[3] regulates the connector, cables and also power delivery features across all uses of USB-C cables, in part^[4] with the USB Power Delivery specification.^[5]

The USB4 standard mandates backwards compatibility to USB 3.x and dedicated backward compatibility with USB 2.0.^[6] The dynamic sharing of bandwidth of a USB4 connection is achieved by encapsulating multiple virtual connections ("tunnels") of other protocols, such as USB 3.x, DisplayPort and PCI Express.

USB4 is based on the Thunderbolt 3 protocol. However, it is different enough that backwards compatibility to Thunderbolt 3 is optional for many device types.^[7]