UK What USB4 is
USB4 is the fourth major generation of the Universal Serial Bus data standard, published by the USB Implementers Forum (USB-IF) in 2019. It runs at 20 or 40 Gb/s, and USB4 Version 2.0, published in 2022, raises that to 80 Gb/s.
USB4 differs from earlier USB in two ways. First, it only works through the USB-C connector, so there is no USB4 version of the rectangular USB-A port. Second, it is built on the Thunderbolt 3 protocol, which Intel contributed to the USB-IF. Instead of sending only USB packets, a USB4 link carries several kinds of traffic in tunnels and shares the bandwidth between them as needed.
The USB-IF now asks manufacturers to label ports by speed, so you may see USB4 ports described as USB 40Gbps or USB 80Gbps on packaging and datasheets.
USB4 vs USB-C
These two are easy to confuse because they always appear together. USB-C is the physical connector: the oval, reversible plug and socket. USB4 is one of the data standards that can run through that connector. Every USB4 port is a USB-C port, but most USB-C ports are not USB4.
A USB-C port on a typical computer may run only USB 2.0 at 480 Mb/s or USB 3.2 at 5 to 20 Gb/s. A USB4 port on the same computer runs at 40 Gb/s and can also drive displays and external PCIe devices. Look for the speed in the datasheet, or the USB 40Gbps logo beside the port, rather than relying on the shape of the socket.
What USB4 can carry
A USB4 link is shared between protocols, each carried in its own tunnel. The host decides how much bandwidth each one gets, so a display does not lock out storage traffic on the same cable.
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USB 3.2 tunnelling. Ordinary USB devices, such as cameras, drives and hubs, work through the USB4 link at their own speed.
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DisplayPort tunnelling. Video for one or more monitors, typically DisplayPort 1.4a on USB4 and up to DisplayPort 2.1 on USB4 Version 2.0.
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PCIe tunnelling. External PCIe devices, such as NVMe enclosures, network adapters and capture devices, appear to the operating system as if they were inside the computer. PCIe tunnelling is optional on basic USB4 hosts, so check before relying on it.
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USB Power Delivery. USB4 requires USB PD, so the same cable can power a monitor or charge a laptop at up to 100 W, or 240 W where both ends support USB PD 3.1.
USB4 speeds compared
USB4 sits alongside Thunderbolt rather than replacing it. Thunderbolt 4 is effectively a USB4 40 Gb/s port with the optional features made mandatory, and Thunderbolt 5 is built on USB4 Version 2.0.
| Interface | Maximum data rate | PCIe tunnelling | Display support | Connector |
|---|---|---|---|---|
| USB 3.2 Gen 2×2 | 20 Gb/s | No | Only via DisplayPort Alt Mode | USB-C |
| USB4 20Gbps | 20 Gb/s | Optional | At least one display | USB-C |
| USB4 40Gbps | 40 Gb/s | Optional | At least one display | USB-C |
| Thunderbolt 4 | 40 Gb/s | Required, 32 Gb/s | Two 4K displays or one 8K | USB-C |
| USB4 Version 2.0 | 80 Gb/s, or 120 Gb/s one way | Optional | Up to DisplayPort 2.1 | USB-C |
Real throughput to a single drive is lower than the line rate, because the link carries protocol overhead and is often shared with a display.
Cables and compatibility
USB4 is backwards compatible with USB 3.2 and USB 2.0 devices, which simply run at their own speed. Many USB4 hosts also accept Thunderbolt 3 devices, but that is optional in the USB4 specification, so it should be confirmed for each computer.
Cables matter more than with earlier USB. A full 40 Gb/s link needs a cable rated USB 40Gbps or a Thunderbolt 4 cable, and passive cables at that rate are typically under a metre long. An ordinary USB-C charging cable will connect, but the link falls back to USB 2.0. If a USB4 link is slower than expected, the cable is the first thing to check, followed by the port’s own rating on the datasheet. Our guide to industrial USB applications covers the earlier USB generations that USB4 stays compatible with.
Where USB4 fits in industrial computing
USB4 is mainly found on compact x86 systems built on recent Intel Core processors. Several of our industrial NUC PCs and 4×4 and NUC motherboards have USB4 ports, which suit applications that need more I/O than a small chassis can hold.
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Extra displays. A USB4 port can drive one or more monitors from a computer that has run out of HDMI or DisplayPort outputs.
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External storage and data offload. Fast NVMe enclosures make it practical to swap recorded data from a vehicle or test rig without opening the computer.
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Expansion without a PCIe slot. PCIe tunnelling can add network, capture or storage devices to a system with no internal slots, where the host supports it.
Quick answers on USB4
USB4: common questions
Is USB4 the same as USB-C?
No. USB-C is the connector and USB4 is a data standard that uses it. All USB4 ports are USB-C, but many USB-C ports only run USB 2.0 or USB 3.2.
Is USB4 the same as Thunderbolt 4?
Close, but not identical. Both run at 40 Gb/s over USB-C and share the same protocol. Thunderbolt 4 makes PCIe tunnelling, two-display support and Thunderbolt 3 compatibility mandatory, while USB4 leaves them optional.
How fast is USB4?
20 or 40 Gb/s, or 80 Gb/s for USB4 Version 2.0. Version 2.0 can also run 120 Gb/s in one direction and 40 Gb/s in the other for high-resolution displays.
Is USB4 backwards compatible?
Yes. USB 3.2 and USB 2.0 devices work in a USB4 port at their own speed. Thunderbolt 3 support is optional on USB4 hosts, so check the datasheet.
What is a USB4 port used for?
High-bandwidth peripherals. Typical uses are docks, monitors, fast external SSDs and PCIe devices, often all through one cable.
We fit and validate USB4 and Thunderbolt peripherals, cables and docks with each system as standard, so the display, storage and expansion you specify run at the speed you expect.