Quick Answer / Summary: A USB 2.0 Type B cable is the A-to-B lead with the square, chamfered plug for peripherals: printers, scanners, audio interfaces, CNC and Arduino boards, lab instruments. It runs 480 Mbps and 500 mA. USB 2.0 B plugs physically fit USB 3.0 B sockets (front section) at reduced speed; USB 3.0 B plugs do not fit USB 2.0 B sockets.
The Type-B plug is the reason USB cables became an office joke – nobody could name the square end. It is also one of the most durable connectors in computing. This page defines the plug, maps its device list, and settles the substitution questions that come up when a shared printer cable goes missing.
Anatomy of the B Plug
Type-B is a square body with two chamfered top corners, four pins, keyed so it inserts one way. The body is larger than any other USB 2.0 plug, which gives it mechanical stability on devices that live on shelves and benches. The related Mini-B and Micro-B are electrically identical, scaled down.
Device Map
Laser and inkjet printers, MFP copiers, flatbed scanners, audio interfaces and mixers, MIDI keyboards, Arduino Uno/Mega, CNC controllers, 3D printer mainboards, laboratory instruments, uninterruptible power supplies with USB monitoring, and receipt printers in the POS class.
USB 3.0 B Sockets and Backward Fits
The USB 3.0 B socket adds a raised section behind the classic B opening for five extra pins. A USB 2.0 A-to-B cable fits that classic opening and runs the device at 480 Mbps – acceptable for printing and scanning. A USB 3.0 B plug’s wider body will not enter a pure USB 2.0 B socket.
Substitution Rules
Safe: USB 3.0 cable into USB 2.0 device (runs at 2.0 speed); USB 2.0 cable into USB 3.0 device (runs at 2.0 speed) when data volume is small. Unsafe: forcing plugs of different families (Mini/Micro), charge-only leads for instruments, and unshielded cable next to printer power supplies.
Type B Cable Substitution Matrix
| Cable in Hand | Device Socket | Result | Verdict |
|---|---|---|---|
| USB 2.0 A-to-B | USB 2.0 B | Full 480 Mbps | Correct |
| USB 2.0 A-to-B | USB 3.0 B | Works at 480 Mbps | OK for print/scan duty |
| USB 3.0 A-to-B | USB 2.0 B | Fits, runs at 480 Mbps | OK |
| USB 3.0 A-to-B | USB 3.0 B | Full 5 Gbps | Correct for 3.0 devices |
| Mini-B / Micro-B | Type-B socket | Does not fit | Never force |
Real-World Application Scenarios
A university print room standardises USB 3.0 A-to-B leads so one stock covers both old and new printers; a maker bench labels each Arduino cable to prevent swap errors; a studio wires its interface with a short ferrited A-to-B to keep the USB ground loop out of recordings.
Recommended Internal Resources
Editorial Note: B-connector cables live in the USB Cables and Cords archive; audio use cases in Audio Cables and Jacks; fleet standards in Commercial USB Cables.
Frequently Asked Questions (FAQ)
Q: What is a USB 2.0 Type B cable for?
A: Connecting host computers to peripheral devices with square B sockets: printers, scanners, audio interfaces, development boards and instruments.
Q: Can I use a USB 2.0 B cable on a USB 3.0 printer?
A: Yes, it fits the classic opening of the 3.0 B socket and runs at 480 Mbps – fine for printing. Only high-volume photo workflows benefit from a true USB 3.0 cable.
Q: Is Type B the same as printer cable?
A: In practice yes: ‘printer cable’ is the consumer name for the A-to-B lead, because printers were the most common B devices.
Q: Why is the B plug so big?
A: Mechanical stability. The larger body anchors firmly to stationary devices, resists levering and survives thousands of reconnections on shared hardware.