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USB-A

USB Standard-A

Standard: USB-IF Last updated: 2025-01-21

USB-A is the original USB connector and remains ubiquitous on host devices. While being phased out in favor of USB-C, it will remain common for years due to the massive installed base. The connector was intentionally designed to be non-reversible to ensure proper power delivery orientation, though this is often cited as a design flaw compared to USB-C's reversibility.

Quick Specifications

Max Speed

10 Gbps

Max Power

4.5W

Pins

9

Reversible

No

⚠️ Common Confusion Points

  • USB 3.x USB-A has 9 pins but is backwards compatible with 4-pin USB 2.0 cables and devices
  • Blue interior usually indicates USB 3.x, but this is a convention not a requirement
  • USB-A ports labeled 'SS' (SuperSpeed) support USB 3.x speeds
  • USB 3.2 Gen 1 was previously called USB 3.0, and USB 3.2 Gen 2 was USB 3.1 - the naming changed in 2019
  • A USB 2.0 cable in a USB 3.x port will only run at USB 2.0 speeds
  • USB-A cannot support USB 3.2 Gen 2x2 (20 Gbps) - that requires USB-C on both ends

Protocols & Versions

Protocol Data Rate Power Max Length
USB 1.1 (1.1) 12 Mbps 2.5W (500mA @ 5V) 5m
USB 2.0 (2.0) 480 Mbps 2.5W (500mA @ 5V), 7.5W with BC 1.2 5m
USB 3.2 Gen 1 (3.2 Gen 1 (formerly USB 3.0)) 5 Gbps 4.5W (900mA @ 5V) 3m
USB 3.2 Gen 2 (3.2 Gen 2 (formerly USB 3.1)) 10 Gbps 4.5W (900mA @ 5V) 1m

USB 1.1 Features

Full Speed Basic data transfer

Cable requirements: Any USB-A cable

USB 2.0 Features

Hi-Speed Charging (BC 1.2)

Cable requirements: Any USB-A cable

USB 3.2 Gen 1 Features

SuperSpeed Blue connector interior

Cable requirements: USB 3.x cable with additional pins

USB 3.2 Gen 2 Features

SuperSpeed+ Teal connector interior (sometimes)

Cable requirements: USB 3.2 Gen 2 rated cable

Connector Specifications

Shape
rectangular
Pins
9 (2 rows)
Width × Height
12 × 4.5 mm
Depth
14 mm
Reversible
No
Pin Pitch
2 mm

Electrical Specifications

Max Voltage
5V
Max Current
0.9A
Max Power
4.5W
Impedance
90Ω differential (SuperSpeed)

Compatibility

Backwards Compatible With

  • USB 1.0
  • USB 1.1

Forward Compatible With

  • USB 3.2 Gen 2

Can Adapt To

  • USB-C
  • Micro USB
  • Mini USB
  • USB-B

Can Adapt From

  • USB-C

Common Uses

  • Desktop computers
  • Laptops (host ports)
  • Wall chargers
  • USB hubs
  • Flash drives
  • Keyboards and mice
  • External hard drives
  • Game controllers

Buying Guide

For USB 3.x speeds, ensure the cable has the blue interior or is explicitly rated for USB 3.0/3.1/3.2. Check for the SuperSpeed (SS) logo. For charging, look for cables rated for higher amperage if using with BC 1.2 chargers. Note that USB-A is limited to 10 Gbps max - for faster speeds, you need USB-C.

Also Known As

USB-A USB Type-A Standard USB

Data Sources