USB Standards and Speeds Explained: USB 1.0 to USB4 Version 2.0

USB 1.0 arrived in 1996 with two speed tiers: Low Speed at 1.5 Mbit/s for simple devices such as mice and keyboards, and Full Speed at 12 Mbit/s for devices such as early scanners and audio interfaces. USB 1.1 followed in 1998, fixing early compatibility problems rather than changing the speed, and became the first version widely adopted by computer manufacturers.

USB 2.0, released in 2000, introduced a High Speed mode at 480 Mbit/s, a large jump that made USB practical for flash drives, printers, external drives and webcams. It remained the mainstream standard for well over a decade and is still used today for low bandwidth devices such as keyboards, mice and many chargers.

USB 3.0, released in 2008, introduced SuperSpeed at 5 Gbit/s. It added extra pins to the Type-A connector and to a new Micro-B SuperSpeed connector used mainly on external hard drives, so a USB 3.0 cable can be told apart from a USB 2.0 one by its extra contacts and, often, a blue plastic insert, although the colour is only a convention and not a requirement.

USB 3.1, released in 2013, is where the renaming began. The existing 5 Gbit/s mode was relabelled USB 3.1 Gen 1, and a new 10 Gbit/s mode was introduced as USB 3.1 Gen 2. Both speeds could appear on either USB-A or the newly arriving USB-C connector.

USB 3.2, released in 2017, renamed both existing tiers again, this time to USB 3.2 Gen 1 and USB 3.2 Gen 2, and added a new two lane mode called USB 3.2 Gen 2x2 that reaches 20 Gbit/s. The 2x2 mode uses both data lanes inside a USB-C cable at once, which is why it only exists over USB-C and never over the older USB-A connector.

USB4, released in 2019, is built on the protocol foundations of Thunderbolt 3, and it only ever appears on USB-C. Depending on the device and the cable, a USB4 connection runs at 20 or 40 Gbit/s, and it can carry video and data over the same port at the same time through a technique called tunneling.

USB4 Version 2.0, released in 2022, raises the ceiling to 80 Gbit/s in both directions at once, or up to roughly 120 Gbit/s in one direction when the other direction is allowed to carry less, an arrangement known as asymmetric mode. It targets demanding uses such as external graphics cards, high resolution or multiple external displays, and fast external storage.

One of the reasons USB has lasted so long is that every generation is designed to work with the ones before it, at least at a basic level. A USB4 laptop port will still charge a device or move files with an old USB 2.0 flash drive, simply falling back to the older, slower signalling that both sides understand. The connection always runs at the highest speed that every part of the chain, meaning the port, the cable and the device, can support together, never faster.

This is worth remembering when a setup performs worse than expected. If a fast USB4 external drive is connected through an old USB 2.0 cable, or through a hub built to an older standard, the entire connection drops down to that slower link, and no setting on the computer will bring the speed back up. The fix is simply to replace whichever part of the chain is the oldest.

Earlier USB generations dedicate a port to a single kind of traffic at a time. USB4 works differently: it can carry several kinds of traffic, such as ordinary USB data, DisplayPort video, and sometimes Thunderbolt native traffic, over the same physical link at the same time, a method called tunneling. The available bandwidth is then shared dynamically between whatever is actually connected, for example a display and a fast storage device plugged into the same dock.

This is what makes a single USB4 cable able to replace several separate cables on a modern desk, driving an external display, charging a laptop and connecting storage devices all at once through one dock. Our guide to hubs and docking stations looks at how this works in a real desk setup, and our guide to USB video and DisplayPort Alt Mode explains how the video side of this sharing works.

For everyday peripherals such as a mouse, keyboard or webcam, even USB 2.0 speed is more than enough, and most such devices are built to that standard on purpose to keep costs down. For external flash drives and hard drives, USB 5Gbps is a comfortable minimum for smooth file transfers. For external SSDs, which can be much faster than mechanical drives, USB 10Gbps or USB 20Gbps makes a noticeable difference. For docking a laptop to multiple high resolution displays, an external graphics enclosure, or very fast external SSD arrays, USB4 at 40 or 80 Gbit/s is the tier to look for.

Our buying guide walks through matching a device, a cable and a port to the speed you actually need, rather than simply buying the highest number available.

Is USB4 the same as Thunderbolt?

USB4 is built on the same underlying protocol ideas as Thunderbolt 3, and the two overlap considerably, but they are not identical. Thunderbolt certification imposes stricter minimum requirements, such as guaranteed 40 Gbit/s support and mandatory external display and external graphics support, while USB4 leaves some of these features optional for manufacturers. Most Thunderbolt devices work on USB4 ports and vice versa, but it is not guaranteed at every speed or with every feature.

Does a higher version number always mean a faster port?

No. Because of the renaming described above, a port labelled USB 3.2 Gen 1 runs at the same 5 Gbit/s as an old USB 3.0 port, not faster. The clearest way to compare two ports or cables is by their actual speed in Gbit/s or by the newer marketing names such as USB 10Gbps, rather than by the version number alone.

What does SuperSpeed mean?

SuperSpeed is the marketing term introduced with USB 3.0 for the 5 Gbit/s tier and, informally, for the family of speeds built on the same underlying SuperSpeed signalling technology. You may still see a SuperSpeed logo or the letters SS printed near a port or on a cable.

Will USB4 Version 2.0 replace USB4?

USB4 Version 2.0 extends USB4 rather than replacing it outright. Devices and cables built for the original 40 Gbit/s USB4 continue to work as before, while newer, more demanding devices adopt the 80 Gbit/s tier as it becomes more common. Expect both to coexist in the market for some years.

How can I tell what speed a cable actually supports?

Physical appearance is not a reliable guide, since many cables of different speeds look alike. Check the packaging, any printed markings near the connector, and the manufacturer specification sheet. Our buying guide lists the labels and certification marks worth checking before you buy.