USB-A connector — specs & speed generations
USB-A is the flat rectangular plug found on chargers, computers, hubs, and countless peripherals. All USB-A generations share the same physical shape, so any USB-A plug fits any USB-A socket — but the speed depends on the slowest component in the chain.
Quick-reference: USB-A speeds
| Generation | Marketing name | Max speed | Port colour (typical) |
|---|---|---|---|
| USB 2.0 | Hi-Speed USB | 480 Mbps | Black or white |
| USB 3.0 | USB 3.2 Gen 1 | 5 Gbps | Blue |
| USB 3.1 Gen 1 | USB 3.2 Gen 1 | 5 Gbps | Blue |
| USB 3.1 Gen 2 | USB 3.2 Gen 2 | 10 Gbps | Red or teal |
Naming confusion: USB 3.0, 3.1, 3.2
The USB-IF renamed USB 3.0 to "USB 3.2 Gen 1" in 2019. If someone says USB 3.0 and 5 Gbps, they mean the same thing. For USB-A you will see:
- 5 Gbps — previously called USB 3.0 or USB 3.1 Gen 1, now called USB 3.2 Gen 1
- 10 Gbps — previously called USB 3.1 Gen 2, now called USB 3.2 Gen 2
USB 3.2 Gen 2×2 (20 Gbps) exists only on USB-C, not USB-A.
Physical dimensions
| Measurement | Value |
|---|---|
| Plug width | 12.0 mm |
| Plug height | 4.5 mm |
| Plug depth | 4.0 mm (pin area) |
| Contacts | 4 (USB 2.0) / 9 (USB 3.x, adds SuperSpeed lanes) |
Backward compatibility
USB-A is fully backward compatible. A USB 3.0 cable plugged into a USB 2.0 port runs at USB 2.0 speeds (480 Mbps). A USB 2.0 device in a USB 3.0 port also runs at USB 2.0 speeds. There is no functional harm — just lower throughput.
Identifying USB-A port speed by colour
Port colour is a manufacturer convention, not an official standard. The common convention:
- Black / white — USB 2.0
- Blue — USB 3.0 / 3.2 Gen 1 (5 Gbps)
- Red or teal — USB 3.1 Gen 2 / 3.2 Gen 2 (10 Gbps), or always-on charging
- Yellow — sleep-and-charge (powers devices when the computer is off)
If the label on the port itself is unclear, check the motherboard or laptop spec sheet for port-by-port speed listings.
When to upgrade to USB-C
USB-A tops out at 10 Gbps on USB-A hardware. USB-C supports USB4 at 40 Gbps and Thunderbolt 4 at 40 Gbps. If you are moving large files frequently or connecting high-bandwidth external storage, a USB-C port is worth seeking. For charging phones, keyboards, mice, and webcams, any USB-A port is adequate. See USB-C vs USB-A.