Is Thunderbolt 4 the same as USB4?
AnswerIt depends
Nearly. Thunderbolt 4 is USB4 at 40 Gbps with every optional feature made mandatory and certified by Intel. A USB4 port can be 20 Gbps, can skip PCIe tunnelling and can support just one display. A Thunderbolt 4 port can't: it guarantees 40 Gbps, 32 Gbps PCIe, two 4K 60 Hz displays and charging. The cables are interchangeable. A Thunderbolt 4 cable is a USB4 40Gbps cable.
| Feature | USB4 (minimum) | Thunderbolt 4 (required) | |
|---|---|---|---|
| Link speed | 20 Gbps | 40 Gbps | |
| PCIe tunnelling (eGPU | fast SSD) | optional | 32 Gbps |
| External displays | one | two 4K 60 Hz, or one 8K | |
| Charging on a computer port | optional | at least one port, up to 100 W | |
| Thunderbolt 3 compatibility | optional | required | |
| Certified by | USB-IF (optional) | Intel (required) |
Buying a laptop? "USB4 40Gbps" plus "PCIe tunnelling" and "two displays" on the spec sheet is effectively Thunderbolt 4 without the badge. Plain "USB4" could be the 20 Gbps minimum.
The standards involved
USB4 (20 and 40 Gbps)
Thunderbolt 3's protocol, opened up as a USB standard. Tunnels USB, DisplayPort and PCIe over one cable.
- data: 20 or 40 Gbps
- video: DisplayPort tunnelled
- power: USB PD required
Thunderbolt 4
The same 40 Gbps as Thunderbolt 3, with the minimums raised so every port behaves the same.
- data: 40 Gbps (PCIe 32 Gbps)
- video: two 4K 60 Hz or one 8K
- power: up to 100 W (USB PD)
Thunderbolt 3
The first Thunderbolt on USB-C. 40 Gbps, but with optional minimums that make ports differ.
- data: 40 Gbps (PCIe 16–32 Gbps)
- video: two 4K 60 Hz
- power: up to 100 W (USB PD)