What Is a USB Pinout? The Complete Wiring Reference
Last updated: June 2026 | Reading time: 12 minutes | WellCircuits Technical Reference
TL;DR / Key Takeaways
- USB 2.0 connectors use 4 pins: VBUS (+5V), D−, D+, GND — standard across all Type-A, Type-B, Mini, and Micro variants
- USB-C uses 24 pins in a symmetrical layout, enabling reversible insertion and power delivery up to 240W
- Standard wire colors (Red/White/Green/Black) are a convention, not a standard — always verify with a multimeter before soldering
- The USB 2.0 differential pair (D+/D−) carries data at signal levels between 0V and 3.3V, encoded via NRZI
- USB 3.0+ adds SuperSpeed pins (SSRX+/−, SSTX+/−) for 5–40 Gbit/s alongside backward-compatible USB 2.0 pins
Introduction: What Is a USB Pinout?
A USB pinout is the standardized mapping of electrical signals to physical connector pins. It tells you exactly which contact does what: where power enters, how data flows, and what serves as the ground reference. Without this mapping, connecting a USB cable to custom hardware is guesswork that often ends in a fried port.
The USB Implementers Forum (USB-IF) defines pin assignments for each connector type. USB 2.0 uses 4 pins. USB 3.0 adds 5 more. USB-C uses 24. Each extra pin unlocks more capability — faster data, higher power, alternate modes like DisplayPort or Thunderbolt.
This guide covers the pinout for every major USB connector type, explains what each wire does, and includes the practical details that generic pinout tables skip: how to verify wire colors with a multimeter, what happens when you get it wrong, and what USB pinout means for PCB design.
What You Need Before Starting
Before working with USB pinouts, gather these:
- Multimeter (with continuity and voltage modes) — wire colors vary between manufacturers
- USB connector diagram for your specific type (Type-A, Type-B, Micro, Mini, or USB-C)
- Soldering iron (if terminating cables or soldering to PCB headers)
- Wire strippers — USB cables typically use 20–28 AWG conductors
- Reference data — USB-IF specifications are publicly available at usb.org
USB 2.0 Pinout: The Foundation
USB 2.0 (Hi-Speed, up to 480 Mbit/s) is the oldest USB standard still in active use. Its 4-pin design became so ubiquitous that the pinout is worth knowing even if you primarily work with USB-C.
USB 2.0 Type-A Pinout
The USB Type-A connector is the rectangular plug found on computers, chargers, and hubs. Here is the pinout:
| Pin | Name | Function | Wire Color (Standard) | Voltage / Signal |
|---|---|---|---|---|
| 1 | VBUS | Bus power supply | Red | +5V DC (max. 500 mA) |
| 2 | D− | Data line negative | White | Differential 0–3.3V |
| 3 | D+ | Data line positive | Green | Differential 0–3.3V |
| 4 | GND | Ground / return path | Black | 0V reference |
USB 2.0 Type-B Pinout
The USB Type-B connector — the squarish plug — is less common in consumer electronics today but remains standard for printers, older peripherals, and some industrial equipment.
| Pin | Name | Function | Wire Color (Standard) |
|---|---|---|---|
| 1 | VBUS | +5V power | Red |
| 2 | D− | Data negative | White |
| 3 | D+ | Data positive | Green |
| 4 | GND | Ground | Black |
**What Most Guides Don't Explain:** Pin numbering differs between the plug (male) and receptacle (female). On a Type-A plug, pins are numbered 1–2–3–4 left to right. On the Type-A receptacle, the numbering appears reversed (4–3–2–1 left to right) because the plug faces into it. The functions still match correctly when mated — the numbering convention simply accounts for the face-to-face orientation.
Mini and Micro USB Pinout (USB 2.0)
Mini and Micro USB connectors add a fifth pin (ID) for USB OTG (On-The-Go), which lets devices act as either a host or a peripheral.
| Pin | Name | Function | Wire Color |
|---|---|---|---|
| 1 | VBUS | +5V power | Red |
| 2 | D− | Data negative | White |
| 3 | D+ | Data positive | Green |
| 4 | ID | OTG host detection (not connected or grounded) | — |
| 5 | GND | Ground | Black |
On standard cables, pin 4 is not connected. On USB OTG adapters, pin 4 is grounded to signal to the device that it should act as a host.
USB 3.0 and USB 3.1 Pinout: Adding SuperSpeed
USB 3.0 (SuperSpeed, up to 5 Gbit/s) added five pins to the original four while maintaining backward compatibility with USB 2.0 devices.
USB 3.0 Type-A Pinout (9 pins total)
| Pin | Name | Function | Wire Color |
|---|---|---|---|
| 1 | VBUS | +5V power (up to 900 mA) | Red |
| 2 | D− | USB 2.0 data negative | White |
| 3 | D+ | USB 2.0 data positive | Green |
| 4 | GND | Ground | Black |
| 5 | SSRX− | SuperSpeed receive negative | Blue |
| 6 | SSRX+ | SuperSpeed receive positive | Yellow |
| 7 | GND_DRAIN | Shield drain wire (uninsulated) | Bare copper |
| 8 | SSTX− | SuperSpeed transmit negative | Violet |
| 9 | SSTX+ | SuperSpeed transmit positive | Orange |
The four original pins (1–4) carry USB 2.0 data and power. Pins 5–9 carry SuperSpeed differential pairs (SSRX and SSTX) and the shield drain wire. USB 3.0 devices use all nine pins; USB 2.0 devices only use the original four.
USB Type-C Pinout: The 24-Pin Standard
USB-C is the most capable USB connector. Its 24-pin symmetrical design enables reversible insertion — the plug works either way up. Every pin has a counterpart on the opposite side, and the Configuration Channel (CC) pins detect orientation automatically.
USB-C Full 24-Pin Layout (Side View, looking into receptacle)
Side A runs top row (A1–A12), Side B runs bottom row (B12–B1) in mirror image.
| Side A Pin | Side B Pin | Name | Function |
|---|---|---|---|
| A1 | B12 | GND | Ground / return path |
| A2 | B11 | SSTX1+ | SuperSpeed transmit pair 1, positive |
| A3 | B10 | SSTX1− | SuperSpeed transmit pair 1, negative |
| A4 | B9 | VBUS | Power (+5V default, up to 48V with USB PD) |
| A5 | B5 | CC1 / CC2 | Configuration Channel — orientation detection, PD negotiation |
| A6 | B7 | D+ | USB 2.0 data positive (shared on both sides) |
| A7 | B6 | D− | USB 2.0 data negative (shared on both sides) |
| A8 | B8 | SBU1 / SBU2 | Sideband Use — audio, Debug Accessory, DisplayPort Alt Mode |
| A9 | B4 | VBUS | Power (second VBUS pin, parallel) |
| A10 | B3 | SSRX1− | SuperSpeed receive pair 1, negative |
| A11 | B2 | SSRX1+ | SuperSpeed receive pair 1, positive |
| A12 | B1 | GND | Ground (second GND pin, parallel) |
The Five Functional Groups of USB-C
Understanding USB-C pinout is easier when you group the 24 pins by function:
1. Power and Ground (4 VBUS + 4 GND pins)
A4, A9, B4, B9 carry VBUS. A1, A12, B1, B12 carry GND. The parallel paths reduce resistance, allowing higher current. Default USB-C delivers 15W (5V, 3A). With USB Power Delivery negotiation over the CC pin, it can reach 240W (48V, 5A) per USB PD 3.1 EPR.
2. USB 2.0 Data Pair (D+ and D−)
A6 and A7 are the USB 2.0 differential pair. Note: B6 and B7 are also labeled D+ and D−, but they are electrically shared — only one orientation’s D+/D− pins carry data, determined by the CC pin orientation detection.
3. SuperSpeed Differential Pairs (4 TX/RX pairs)
A2/A3 (SSTX1+/−), A10/A11 (SSRX1+/−) on one orientation, B2/B3 (SSRX2+/−), B10/B11 (SSTX2+/−) on the other. These four pairs enable USB 3.2 (up to 20 Gbit/s) and USB4 (up to 40 Gbit/s). USB4 Gen 3×2 uses both TX/RX pairs in both directions simultaneously.
4. Configuration Channel (CC1, CC2)
The CC pins detect cable orientation and negotiate USB Power Delivery. When you plug in a USB-C cable, the CC pin on the correct side goes active — this tells the device which side’s SuperSpeed pairs to use. Without functional CC pins, USB-C falls back to basic 5V charging at default current.
5. Sideband Use Pins (SBU1, SBU2)
These auxiliary pins carry alternate mode signals — DisplayPort, Thunderbolt, or Debug Accessory Mode. They are idle in standard USB data/charging applications.
How to Wire a USB Connector: Step-by-Step
Wiring a USB connector correctly is a matter of matching each wire to its pin. Here is the practical process:
Step 1 — Strip and Inspect the Cable
Remove the outer jacket carefully (about 2 cm). Inside a standard USB 2.0 cable, you will find four wires plus a drain wire and shield:
- Red → VBUS (+5V)
- White → D− (data negative)
- Green → D+ (data positive)
- Black → GND (ground)
USB 3.0 cables add five more wires: Blue, Yellow, bare drain wire, Violet, and Orange for SuperSpeed pairs.
**Common Mistake to Avoid:** Non-standard wire colors are common. A 2017 survey of USB cables found that approximately 15–20% of aftermarket USB cables used non-standard color coding. Red is almost always VBUS, but D+ and D− swap frequently between manufacturers. Always verify with a multimeter before powering a device.
Step 2 — Verify Wire Identity with a Multimeter
Set your multimeter to continuity mode. Touch one probe to each exposed wire and the other probe to the corresponding pin on the USB connector. Pin numbering is printed on most connector housings.
| If you want to find… | Continuity test between… |
|---|---|
| VBUS | Red wire → Pin 1 on connector |
| GND | Black wire → Pin 4 on connector |
| D+ | Green wire → Pin 3 on connector |
| D− | White wire → Pin 2 on connector |
Alternatively, with the cable disconnected at both ends, measure resistance between pins: the D+/D− pair will show approximately 90Ω differential impedance (within tolerance). VBUS to GND will show near zero resistance.
Step 3 — Solder Each Wire to Its Pin
Use a temperature-controlled soldering iron (recommended: 350°C for USB connectors). Pre-tin both the wire and the pin pad. Apply solder to the joint — a proper USB solder joint takes 2–3 seconds of contact. Avoid bridging between adjacent pins, especially on USB-C where 24 pins are packed into a small footprint.
**B类 ANGLE — Lessons from the Factory:**
At WellCircuits, we see USB connector rework regularly. The most common failure is cold solder joints on the D+/D− pins, which causes intermittent device recognition — the device charges but does not sync data. A visual inspection is not enough; a continuity test after soldering catches this before the connector is assembled into the housing.
Step 4 — Test Before Assembly
Before closing the connector housing, test with a USB cable tester or by connecting the device to a computer. Check for:
- +5V on VBUS (within ±5% tolerance: 4.75V–5.25V)
- D+/D− within 0V–3.3V range
- Continuity from GND to connector shell (grounded)
- No shorts between adjacent pins
Step 5 — Assemble and Final Test
Once the housing is closed, perform a final functional test. For USB-C, test insertion in both orientations — if only one orientation works for data, the CC pin may not be correctly connected.
USB Wire Color Code: What the Colors Mean
While wire colors follow a convention, they are not enforced by any standard. Here is what the colors typically mean:
| Wire Color | USB 2.0 Function | USB 3.0 Function | USB-C Function |
|---|---|---|---|
| **Red** | VBUS (+5V) | VBUS (+5V) | VBUS (A4, A9, B4, B9) |
| **White** | D− | D− | D− (A7 / B6) |
| **Green** | D+ | D+ | D+ (A6 / B7) |
| **Black** | GND | GND | GND (A1, A12, B1, B12) |
| **Blue** | — | SSRX− | — |
| **Yellow** | — | SSRX+ | — |
| **Violet** | — | SSTX− | — |
| **Orange** | — | SSTX+ | — |
| **Bare copper** | Shield (drain) | GND_DRAIN | Shield drain |
| **Blue (CC)** | — | — | CC1/CC2 (A5 / B5) |
| **No color** | — | — | SBU1/SBU2 (A8 / B8) |
**Wire colors are a convention, not a standard.** The USB specification does not mandate wire colors. Counterfeit cables, OEM cables, and cables from different regions frequently use non-standard colors. Always use a multimeter for verification in any production, repair, or custom wiring application.
USB Connector Types Comparison
| Feature | USB 2.0 Type-A | USB 2.0 Type-B | Mini USB | Micro USB | USB Type-C |
|---|---|---|---|---|---|
| Pins | 4 | 4 | 5 | 5 | 24 |
| Max data speed | 480 Mbit/s | 480 Mbit/s | 480 Mbit/s | 480 Mbit/s | 40 Gbit/s (USB4) |
| Max power (default) | 2.5W | 2.5W | 2.5W | 2.5W | 15W |
| Max power (PD) | N/A | N/A | N/A | N/A | 240W |
| Reversible | No | No | No | No | Yes |
| OTG support | No | No | Yes (pin 4) | Yes (pin 4) | Yes (CC pin) |
| Physical size | Large | Medium | Small | Very small | Compact |
**A类 ANGLE — What the Specs Don't Tell You:**
The USB 2.0 differential pair (D+/D−) is designed for 90Ω differential impedance. On a PCB, trace width and spacing must be controlled to maintain this impedance — deviation causes signal reflections that degrade data integrity at high speeds. At 480 Mbit/s, USB 2.0 is sensitive to impedance mismatches, which is why well-designed USB ports often include series termination resistors (typically 22–33Ω) near the connector.
Why USB Pinout Matters for PCB Design
Understanding USB pinout is essential for hardware designers working with USB-C or USB 3.0 on PCBs. The connector pinout determines your trace routing strategy.
High-Speed Differential Pair Routing
D+/D− (USB 2.0) and the SuperSpeed pairs (SSRX+/−, SSTX+/−) are differential pairs. PCB routing requirements:
- D+/D−: 90Ω differential impedance, ±5% tolerance. Keep trace lengths matched within 0.15 mm to prevent skew.
- SuperSpeed pairs: 90Ω differential impedance for USB 3.0 (5 Gbit/s). For USB4 (10–40 Gbit/s), impedance tolerance tightens to ±3%.
- Route on inner layers when possible for better impedance control and EMI shielding.
Power Delivery Considerations
USB PD negotiation happens over the CC pins. On your PCB, include:
- CC1 and CC2 pull-up resistors (56kΩ to VBUS) for Source mode
- CC1 and CC2 pull-down resistors (5.1kΩ to GND) for Sink mode
- USB PD controller IC (e.g., FUSB302, RT1715) for full PD implementation
Thermal Management
At high power delivery (100W+), USB-C connectors and PCB traces dissipate significant heat. Design thermal vias near the connector footprint and use heavier copper weights (2oz+) for power traces carrying high current.
**B类 ANGLE — What We've Seen in Production:**
The most common USB-C design issue we encounter in DFM reviews is inadequate thermal relief on the VBUS and GND pins. When a board is expected to deliver 60–100W, a standard 0.3mm pad with a few thermal vias is insufficient. We recommend multiple thermal vias (minimum 4) under each power pad and a minimum of 2oz copper on power planes serving USB PD circuits.
What WellCircuits Has Learned After Manufacturing USB-Enabled Boards
C类 ANGLE — Honest Reflection:
When USB-C connectors first became mainstream around 2015, we saw a wave of prototype boards come through our facility with USB-C footprints that were almost — but not quite — correct. The CC pin routing was the most common issue. Designers knew USB-C was reversible, but they wired only one CC pin or forgot pull-up/pull-down resistors entirely. The result: the connector looked right, but the device defaulted to basic 5V charging with no data and no power negotiation.
That pattern taught our team to always ask about USB-C CC pin implementation during DFM review, regardless of what the designer thought they had already verified. It is one of those details that is easy to assume is correct until it is not.
The lesson that has stayed with us: in USB design, “good enough” is a moving target. What worked at 5W fails at 100W. What worked at 480 Mbit/s fails at 10 Gbit/s. The pinout is the same, but the margin for error shrinks dramatically as power and speed increase.
Frequently Asked Questions
Q: What is the USB 2.0 pinout?
The USB 2.0 pinout assigns 4 pins: Pin 1 = VBUS (+5V, up to 500 mA), Pin 2 = D− (data negative), Pin 3 = D+ (data positive), Pin 4 = GND (ground). This applies to Type-A, Type-B, Mini, and Micro USB connectors. The same pin functions apply across all USB 2.0 connector types — only the physical shape differs.
Q: How do I identify USB wire colors without a multimeter?
You cannot reliably identify USB wires by color alone — there is no standard enforcing color codes. Red is almost always VBUS, and Black is almost always GND. D+ and D− (White and Green) are less reliable. The safest approach is to use a multimeter in continuity mode: connect one probe to a pin on the connector end and touch the other probe to each wire at the cable’s other end until you find continuity.
Q: What is the USB Type-C pinout?
USB-C uses 24 pins organized in two mirrored rows of 12. Key pins: VBUS (A4, A9, B4, B9) for power delivery; GND (A1, A12, B1, B12) for ground; D+/D− (A6/A7) for USB 2.0 data; four SuperSpeed pairs (A2/A3, A10/A11, B2/B3, B10/B11) for high-speed data; CC1/CC2 (A5/B5) for orientation detection and USB PD negotiation; SBU1/SBU2 (A8/B8) for alternate mode signaling.
Q: Can I use a USB-C cable on a USB 2.0 device?
Yes. USB-C is backward compatible with USB 2.0. When a USB-C cable connects to a USB 2.0 device, only the D+/D− pins and VBUS/GND are used. The SuperSpeed pairs and CC pins are idle. USB-C to USB-A adapters work the same way — they expose only the USB 2.0 pinout through the Type-A connector.
Q: What is the maximum power USB-C can deliver?
USB-C without Power Delivery delivers up to 15W (5V, 3A). With USB Power Delivery 3.1 Extended Power Range (EPR), it supports up to 240W (48V, 5A). This requires EPR-capable cables (marked 5A) with embedded E-marker chips. Standard USB-C cables without E-markers are limited to 3A.
Conclusion
Understanding USB pinout means understanding that every USB connector — from the humble 4-pin USB Type-A to the 24-pin USB-C — maps specific electrical functions to specific physical pins. VBUS always carries power, D+ and D− always carry data, and GND always provides the reference.
The practical skill is not memorizing every variant — it is knowing how to verify. A multimeter is more reliable than a wire color chart. A connector datasheet is more authoritative than a forum post. And for PCB designers, knowing why those pins are assigned the way they are — impedance control, thermal management, CC pin negotiation — separates a working design from one that passes visual inspection but fails in the field.
WellCircuits handles USB-enabled PCB manufacturing daily — from simple USB 2.0 control boards to complex USB4 devices with high-power delivery. Our engineering team provides free DFM reviews for orders, catching USB connector and routing issues before they become production problems.
Need help designing a USB-C or USB 3.0 board that will actually work? Talk to WellCircuits’ Engineering Team →
Author: WellCircuits Technical Team
Industry: PCB Manufacturing & Assembly
Last Updated: June 2026
Sources: USB-IF (usb.org), USB 2.0 Specification, USB Power Delivery 3.1, IPC Standards
