USB4 is based on the Thunderbolt 3 protocol specification. It supports 20 Gbit/s throughputs, is compatible with Thunderbolt 3, and backward compatible with USB 3.2 and USB 2.0.

The architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application.

USB4™ identifies two transfer rates, USB4™ 20Gbps at 20Gbps and USB4™ 40Gbps at 40Gbps.

Marketing name: USB4™ 20Gbps
• Product capability: product signals at 20Gbps
Marketing name: USB4™ 40Gbps
• Product capability: product signals at 40Gbps

USB4™ Key Points:
• Two-lane operation using existing USB Type-C® cables
• Doubles the bandwidth to extend USB Type-C® performance
• Up to 40Gbps operation over 40Gbps-certified cables
• Enables multiple simultaneous data and display protocols
• Multiple data and display protocols efficiently share the total available bus bandwidth
• USB4™ hosts can optimally scale allocations for display data flow
• Backward compatibility with USB 3.2, USB 2.0 and Thunderbolt 3

The USB4™ specification compliments and build upon the existing USB 3.2 and USB 2.0 specifications. The USB4™ architecture defines a method to share a single high-speed link with multiple end device types dynamically that best serves the transfer of data by type and application.
As the USB Type-C® connector has evolved into the role of the external display port of many host products, the USB4™ specification provides the host the ability to optimally scale allocations for display data flow. Even as the USB4™ specification introduces a new underlying protocol, compatibility with existing USB 3.2, USB 2.0 and Thunderbolt 3 hosts and devices is supported; the resulting connection scales to the best mutual capability of the devices being connected.