USB without the confusion – versions, speeds, connectors and Thunderbolt
How to make sense of the USB 2.0, USB 3.2, USB4 and Thunderbolt labels, the difference between a connector and an interface, and how to find out what a port and cable can really do.
The short version
- The connector (USB-A, USB-C) and the interface (USB 2.0, USB 3.2, USB4, Thunderbolt) are two different things. A USB-C port can be slow USB 2.0 or 80 Gb/s.
- USB-IF recommends labelling the speed directly – "USB 5Gbps", "USB 10Gbps", "USB 20Gbps", "USB 40Gbps", "USB 80Gbps".
- Devices agree on the highest speed they have in common. A slow cable or port slows down the whole chain.
Connector vs interface
The connector is the shape: USB-A (a rectangle that only goes in one way), USB-C (oval, symmetrical), micro-USB and others. The interface is what travels through the connector, and at what speed.
The USB-C connector is now on most new devices, but behind it can be anything from USB 2.0 to Thunderbolt 5. Likewise, USB-A can be 480 Mb/s or 10 Gb/s.
Speeds according to the specifications
| Interface | Theoretical maximum | USB-IF recommended label |
|---|---|---|
| USB 2.0 | 480 Mb/s | – |
| USB 3.2 Gen 1 | 5 Gb/s | USB 5Gbps |
| USB 3.2 Gen 2 | 10 Gb/s | USB 10Gbps |
| USB 3.2 Gen 2×2 | 20 Gb/s (two lanes, USB-C only) | USB 20Gbps |
| USB4 (version 1) | 40 Gb/s | USB 40Gbps |
| USB4 version 2.0 | 80 Gb/s | USB 80Gbps |
| Thunderbolt 4 | 40 Gb/s | – |
| Thunderbolt 5 | 80 Gb/s, with Bandwidth Boost 120 Gb/s | – |
USB-IF states that the USB 3.2 specification absorbed all previous 3.x versions and has three speeds – 5, 10 and 20 Gb/s. That is why the same port could in the past be called “USB 3.0”, “USB 3.1 Gen 1” or “USB 3.2 Gen 1”. Chipset makers now use clearer names – AMD, for example, writes “SuperSpeed USB 5Gbps / 10Gbps / 20Gbps” in its AM5 chipset table.
We list Thunderbolt 4 at 40 Gb/s based on Intel’s press release for Thunderbolt 5, which according to Intel brings double the total bidirectional bandwidth of Thunderbolt 4 (80 Gb/s).
Real-world speed is always lower. Part of the bandwidth goes on encoding and protocol overhead, and the device itself (the drive, the controller in the enclosure, the hub) also affects the speed.
The highest common speed
USB is backwards compatible. Connect a USB 10Gbps device to a USB 5Gbps port and it runs at 5 Gb/s. Use a USB-C cable that only carries USB 2.0 (common with cheap charging cables) and everything runs at 480 Mb/s – even if both the port and the drive can do more.
Video and charging
USB-C can also carry video (DisplayPort Alt Mode, or tunnelled DisplayPort in USB4 and Thunderbolt) and charging via USB Power Delivery up to 240 W. Neither is mandatory on every port, though. Check the device’s specification to see which ports support what.
Where to look
- The technical specification from the laptop or motherboard maker (look for the table of ports).
- Icons next to the port: the DisplayPort logo, the Thunderbolt lightning bolt, the speed marking.
- The cable’s packaging: data speed and power rating (60 W / 100 W / 240 W).
You can compare all the interfaces on one axis with the Interface speeds tool, and the connector shapes in the connector atlas.
Before you finish
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Notes and sources
- USB-IF: USB 3.2 Specification – 5, 10 and 20 Gb/s speeds
- USB-IF: USB4 Specification
- USB Promoter Group: USB4 Version 2.0 – announcement (up to 80 Gb/s)
- Intel: Intel Introduces Thunderbolt 5 (80 Gb/s, Bandwidth Boost 120 Gb/s)
- AMD: AMD Socket AM5 Chipset – chipsets, PCIe lanes, USB
- AMD: AMD Ryzen 9 9950X – specifications (TDP 170 W, AM5, DDR5)
- USB-IF: USB Charger (USB Power Delivery) – up to 240 W
We opened every link above and compared the figures on 12 October 2026. The pages belong to their publishers and can change after that date.
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