USB versions decoded
USB naming is famously confusing — the same 5 Gbit/s standard has been called USB 3.0, USB 3.1 Gen 1, and USB 3.2 Gen 1 over the years. This reference lists every major USB specification with its original marketing name, its current USB-IF name, the maximum signalling rate, effective throughput, power delivery limit, and which connectors it uses.
How it works
A USB standard defines two largely independent things: the data rate and the power it can carry. The advertised rate (for example 10 Gbit/s) is the raw signalling speed. To get usable throughput you subtract line-encoding overhead. USB 3.0 uses 8b/10b encoding, costing 20%, so 5 Gbit/s becomes roughly 500 MB/s. From 10 Gbit/s onward USB switched to 128b/132b encoding, which costs only about 3%, so 10 Gbit/s yields about 1.2 GB/s.
Power is negotiated separately through USB Power Delivery (PD). Without PD, a port supplies a fixed 2.5–4.5 W. With PD over a USB-C cable, the source and sink negotiate a contract up to 100 W (PD 3.0) or 240 W (PD 3.1, using up to 48 V). The connector and the data standard are also independent: a USB-C port can run anything from USB 2.0 to USB4 80 Gbps.
Tips and notes
- When buying a cable, check both the data rating and the power rating — many cheap USB-C cables only carry USB 2.0 data even though they fit any USB-C port.
- USB4 and Thunderbolt 4 share the USB-C connector and the 40 Gbit/s tier, and USB4 can tunnel PCIe, DisplayPort, and USB 3.2 traffic over the same link.
- “Gen 2x2” means two 10 Gbit/s lanes bonded for 20 Gbit/s, which is why it requires the USB-C connector that exposes both lane pairs.
- For charging, the cable must support the wattage; 240 W PD 3.1 requires an EPR-rated (Extended Power Range) cable.