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.
The naming history in plain English
The USB Implementers Forum (USB-IF) has rebranded SuperSpeed USB multiple times, which is the source of most confusion:
| Original name | Intermediate name | Current USB-IF name | Speed |
|---|---|---|---|
| USB 3.0 | USB 3.1 Gen 1 | USB 3.2 Gen 1 | 5 Gbit/s |
| USB 3.1 Gen 2 | USB 3.1 Gen 2 | USB 3.2 Gen 2 | 10 Gbit/s |
| (new in 3.2) | — | USB 3.2 Gen 2×2 | 20 Gbit/s |
| — | — | USB4 Gen 2×2 | 20 Gbit/s |
| — | — | USB4 Gen 3×2 | 40 Gbit/s |
| — | — | USB4 80 Gbps (v2) | 80 Gbit/s |
Product boxes often use the simple marketing names (SuperSpeed 5, SuperSpeed 10, etc.) rather than the Gen nomenclature. The reference tool maps all of these so you can decode what any product actually does.
Data rate vs. real throughput
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 / 3.2 Gen 1 (5 Gbit/s) uses 8b/10b encoding, with 20% overhead. Effective throughput: ~500 MB/s.
- USB 3.2 Gen 2 (10 Gbit/s) and faster uses 128b/132b encoding, with only ~3% overhead. Effective: ~1.2 GB/s at 10 Gbit/s.
- USB4 Gen 3×2 (40 Gbit/s) uses the same efficient encoding. Effective: ~4 GB/s.
Power delivery: connectors vs. standards
Power is negotiated separately through USB Power Delivery (PD). The data speed and the charging wattage are independent features:
| Charging method | Max wattage | Requirement |
|---|---|---|
| USB 2.0 (no PD) | 2.5 W | Any USB port |
| USB-C without PD | 7.5–15 W | USB-C port |
| USB PD 3.0 | 100 W | USB-C + PD cable |
| USB PD 3.1 (EPR) | 240 W | USB-C + EPR cable |
A phone charger rated “65 W USB-C” uses USB PD to negotiate that wattage; the underlying data standard might only be USB 2.0 for all the phone cares. The connector and the data standard are independent: a USB-C port can run anything from USB 2.0 data to USB4 80 Gbps.
USB4 and Thunderbolt 4
USB4 and Thunderbolt 4 are closely related. Thunderbolt 4 is Intel’s branded certification for USB4 Gen 3×2 (40 Gbit/s) with stricter minimum requirements (mandatory PCIe tunneling, minimum display and charging specs). All Thunderbolt 4 ports are USB4 compatible, but not all USB4 ports are Thunderbolt 4. USB4 can tunnel PCIe, DisplayPort, and USB 3.2 traffic over the same physical link.
Practical buying guidance
- Check both ratings on a cable: data speed and wattage are separate. Many inexpensive USB-C cables only carry USB 2.0 data (480 Mbit/s) despite fitting any USB-C port. If you need 10 Gbit/s transfers, the cable must be rated for it.
- “Gen 2×2” requires USB-C: the 20 Gbit/s bonded mode uses two 10 Gbit/s lanes and only works with USB-C, which exposes both lane pairs. Type-A connectors max out at USB 3.2 Gen 2 (10 Gbit/s).
- 240 W PD 3.1 needs an EPR (Extended Power Range) cable — regular PD 3.0 cables are only certified to 100 W and should not be used with EPR chargers at full power.
- USB4 80 Gbps (v2) requires both a capable port and a compatible cable — most current peripherals do not yet support this tier.