What is USB4?
USB4 is the latest generation of the USB specification, designed by the USB Promoter Group using Thunderbolt 3 technology as its foundation. It exclusively uses the USB-C connector and delivers data transfer speeds of up to 40 Gbps (USB4 Gen 3x2) or 80 Gbps (USB4 Version 2.0). Beyond raw speed, USB4 consolidates data transfer, DisplayPort video output, and USB PD power delivery into a single cable through an intelligent bandwidth-sharing mechanism, making it the most capable and versatile USB standard ever released.
In-Depth
Tunneling: One Cable, Multiple Protocols
The defining innovation of USB4 is tunneling, which allows data (USB), display (DisplayPort), and PCIe signals to travel simultaneously over one physical connection. Bandwidth is allocated dynamically: if you are only transferring files, the full bandwidth goes to data; if you plug in a monitor, the system carves out enough bandwidth for the display and gives the remainder to data. This eliminates the need for separate cables for video, data, and charging.
USB4 Version Comparison
| Version | Max Speed | Highlights |
|---|---|---|
| USB4 Gen 3x2 | 40 Gbps | Thunderbolt 3 compatible; baseline spec |
| USB4 Version 2.0 | 80 Gbps | Asymmetric mode enables up to 120 Gbps one-way |
| Thunderbolt 4 | 40 Gbps | USB4-compatible + Intel-certified quality |
| Thunderbolt 5 | 80 Gbps | USB4 v2.0 based + up to 120 Gbps |
USB4 Version 2.0 introduces an asymmetric mode that concentrates up to 120 Gbps of bandwidth in one direction, which is invaluable for external GPUs (eGPUs) and high-resolution multi-monitor setups that demand massive downstream throughput.
USB4 and Thunderbolt: The Relationship
Because USB4 is built on Thunderbolt 3, it is broadly compatible with Thunderbolt 3 and 4 devices. However, the USB4 specification makes Thunderbolt support optional for manufacturers, meaning not every USB4 port will recognize every Thunderbolt peripheral. If you need guaranteed Thunderbolt compatibility, choose a port or device that carries Intel’s official Thunderbolt 4 or 5 certification.
How to Choose
1. Determine Your Speed Requirements
For everyday external SSD file transfers, 40 Gbps (USB4 Gen 3x2) is more than sufficient. If you plan to connect an eGPU, drive 8K displays, or run multiple high-resolution monitors, USB4 Version 2.0 or Thunderbolt 5 at 80 Gbps is the better investment.
2. Verify Cable Ratings
A cable certified for 40 Gbps cannot achieve 80 Gbps, regardless of the port it is plugged into. Always match the cable’s certified speed to your needs. Shorter cables (0.8 m or less) are more reliable at peak speeds. Check manufacturer specifications rather than relying on appearance, since USB4 cables look identical to slower USB-C cables.
3. Confirm Peripheral Compatibility
USB4 ports are backward compatible with USB 3.x and USB 2.0 devices, but speeds will be limited to the device’s maximum. When building a USB4-centric setup, consider a USB4 docking station or hub that can distribute the bandwidth to multiple high-speed peripherals efficiently.
The Bottom Line
USB4 represents the convergence of data, video, and power into a single, high-speed standard. Whether you choose the 40 Gbps baseline or the 80 Gbps Version 2.0, USB4 future-proofs your connectivity for years to come. Match your speed tier to your actual use case, invest in properly rated cables, and confirm Thunderbolt compatibility if you rely on Thunderbolt peripherals. With USB4, one port and one cable can genuinely do it all.