The USB Promoter group has recently announced the specifications for USB 4 which will bring a range of improvements to USB 3.2 and USB 2. USB 4 is based on Thunderbolt architecture which doubles the bandwidth of the current USB technology and can handle multiple data and display protocols at the same time. 

It will look like USB-C but boast data-transfer speeds equivalent to Intel's Thunderbolt 3 version of USB-C.

Most of us are still using adaptors to make our USB-A devices compatible with USB-C ports, so yet another version of USB arriving sounds daunting. Here is what you need to know about USB 4.

How is USB 4 different to USB 3.2 and USB 2?

  • Up to 40 Gbps data transfer speed using two-lane cables, matching the speed of Thunderbolt 3
  • Better video performance thanks to the technology intelligently allocating resources based upon transfer demand
  • Thunderbolt 3 compatible depending on how the USB 4 technology is implemented
  • Will use Type-C ports

What are the different versions of USB-C?

There's a bunch of types of USB, each with a couple of names and data-transfer speeds. Here's an explanation of each to help you out.

  • SuperSpeed USB aka USB 3.1 Gen 1 aka USB 3.2 1: 5Gbps
  • SuperSpeed USB 10Gbps aka USB 3.1 Gen 2 aka USB 3.2 2: 10Gbps
  • SuperSpeed USB 20Gbps aka USB 3.2 2x2: 20Gbps
  • Thunderbolt 3: 40Gbps
  • USB 4 (coming in 2020): 40Gbps

USB-C specs

USB 4 and Thunderbolt 3 compatibility

Intel, the developer and owner of the Thunderbolt 3 protocol, has provided it to the USB Promoter Group to allow the upcoming USB 4 platform to be compatible with Thunderbolt 3 devices. While this is great news for consumers generally, manufacturers will not be obliged to implement Thunderbolt 3 functionality into their USB 4 specs, so you could well end up with a USB 4 enabled device that won’t be compatible with Thunderbolt 3. As ever, it’s important to check the exact specification of the device you’re purchasing before you put down your hard-earned money.

While the promise of 40 Gbps transfer speeds looks great on paper, not every USB device will be able to meet that speed, so USB 4 devices might have to lower their speed to accommodate the hardware they're connected to. There will be three speeds available to USB 4 (10Gbps 20Gbps and 40Gbps) and you can usually expect the smaller and less expensive devices to be capped at the lower transfer speeds.

USB 4 intelligent bandwidth sharing

USB-C introduced a feature called “alternative mode” which allows input from DisplayPort and HDMI from a USB-C port, but the current technology doesn’t allow for an efficient way of splitting resources if you’re also transferring both data and video at the same - it will divide the bandwidth between the two streams of information granting 50% bandwidth to each.

USB 4 will intelligently allocate resources to video and data streams based on demand, so if you’re streaming 4k video and transferring files at the same time, the technology will do its best to balance these needs out to keep both data streams running smoothly.

USB 4 will support USB Power Delivery

Only certain USB-C ports support USB Power Delivery (USB PD), which is a requirement for charging some devices including laptops. Every USB 4 device and port will support USB PD as standard with the ability to support up to 100 watts, although no charging device will provide anything close to that amount of power just yet.

USB 4 will also be backwards compatible with USB 3 and 2 devices, although you will be limited to the speed of the older versions if they do interact. A USB 4 external drive will not gain USB 4 speeds if it interfaces to a device via a USB 2 or 3 port.

When is USB 4 coming out?

USB 4 won’t release until later this year and it will be at least another year before we start seeing it appear in consumer products, so it will be late 2020 or early 2021 before you’ll have to worry about it. More details around the technology will also emerge over that time, but it’s already looking like a promising step forward.

If you're still struggling with the switch from USB-A to USB-C then getting an adaptor will make your life much easier.