Which pin is +5 V on a USB connector?

Pin 1 (VBUS) on every pre-USB-C connector: Type-A, Type-B, Mini-B, Micro-B and their USB 3 versions. Ground is pin 4 on A and B, pin 5 on Mini and Micro.

What are the wire colors in a USB cable?

In a standard USB 2.0 cable: red for VBUS, white for D−, green for D+, black for ground. Cheap cables do not always follow the code, so check with a multimeter before soldering.

What is the Micro-USB ID pin for?

It sets the role in USB On-The-Go. An OTG cable ties ID to ground at the A plug end: the device that receives it switches to host mode and powers the peripheral. Floating, the device stays a peripheral.

Does a USB 2.0 cable work in a USB 3 port?

Yes. USB 3 Standard-A, Standard-B and Micro-B receptacles accept the matching USB 2.0 plugs, and the link simply falls back to USB 2.0. The reverse fails for Type-B: the taller USB 3 Standard-B plug does not fit a USB 2.0 B receptacle.

Pinout

USB-A, USB-B, Mini-USB and Micro-USB pinout

The USB connectors that came before USB-C share the same USB 2.0 core: VBUS, D−, D+ and ground, on pins 1 to 4. Mini-B and Micro-B add an ID pin for USB On-The-Go, and USB 3 adds two SuperSpeed pairs and a drain ground.

By Hugues Orgitello · Updated October 14, 2026 ·

USB 2.0 Type-A and Type-B, 4 pins

Same numbering on plug and receptacle, Type-A and Type-B alike. Colors are the wire colors of a standard USB 2.0 cable.

Pin	Signal	Dir.	Wire	Description
1	VBUS		Red	+5 V power (Power)
2	D-	I/O	White	USB 2.0, negative (Differential pair)
3	D+	I/O	Green	USB 2.0, positive (Differential pair)
4	GND		Black	Ground (Ground)

Mini-B and Micro-B, 5 pins

Mini-B and Micro-B use the same assignment. The ID pin tells host from device in USB On-The-Go.

Pin	Signal	Dir.	Description
1	VBUS		+5 V power (Power)
2	D-	I/O	USB 2.0, negative (Differential pair)
3	D+	I/O	USB 2.0, positive (Differential pair)
4	ID	In	OTG identification: floating on a B plug (device), grounded on an A plug (host) (Configuration)
5	GND		Ground (Ground)

USB 3.x Standard-A, 9 pins

Pins 1 to 4 stay the USB 2.0 interface, which keeps backward compatibility. Pins 5 to 9 form a second row: in the receptacle their SuperSpeed blades sit at the front and the USB 2.0 contacts at the back; in the plug it is the other way round. TX and RX are seen from the host that carries the A receptacle.

Pin	Signal	Dir.	Description
1	VBUS		+5 V power (Power)
2	D-	I/O	USB 2.0, negative (Differential pair)
3	D+	I/O	USB 2.0, positive (Differential pair)
4	GND		Power ground (Ground)
5	StdA_SSRX-	In	SuperSpeed receive, negative (Differential pair)
6	StdA_SSRX+	In	SuperSpeed receive, positive (Differential pair)
7	GND_DRAIN		Signal return ground (drain) (Ground)
8	StdA_SSTX-	Out	SuperSpeed transmit, negative (Differential pair)
9	StdA_SSTX+	Out	SuperSpeed transmit, positive (Differential pair)

USB 3.x Standard-B, 9 pins

TX and RX are seen from the device that carries the B receptacle: its transmit pair lands on the host receive pair.

Pin	Signal	Dir.	Description
1	VBUS		+5 V power (Power)
2	D-	I/O	USB 2.0, negative (Differential pair)
3	D+	I/O	USB 2.0, positive (Differential pair)
4	GND		Power ground (Ground)
5	StdB_SSTX-	Out	SuperSpeed transmit, negative (Differential pair)
6	StdB_SSTX+	Out	SuperSpeed transmit, positive (Differential pair)
7	GND_DRAIN		Signal return ground (drain) (Ground)
8	StdB_SSRX-	In	SuperSpeed receive, negative (Differential pair)
9	StdB_SSRX+	In	SuperSpeed receive, positive (Differential pair)

USB 3.x Micro-B, 10 pins

The USB 3 Micro-B plug puts a USB 2.0 Micro-B section (pins 1 to 5) next to a SuperSpeed section (pins 6 to 10). A USB 2.0 Micro-B plug fits the USB 3 receptacle.

Pin	Signal	Dir.	Description
1	VBUS		+5 V power (Power)
2	D-	I/O	USB 2.0, negative (Differential pair)
3	D+	I/O	USB 2.0, positive (Differential pair)
4	ID	In	OTG identification (Configuration)
5	GND		Power ground (Ground)
6	MicB_SSTX-	Out	SuperSpeed transmit, negative (Differential pair)
7	MicB_SSTX+	Out	SuperSpeed transmit, positive (Differential pair)
8	GND_DRAIN		Signal return ground (drain) (Ground)
9	MicB_SSRX-	In	SuperSpeed receive, negative (Differential pair)
10	MicB_SSRX+	In	SuperSpeed receive, positive (Differential pair)

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Design notes

D+ and D− are a 90 Ω differential pair. At Full Speed (12 Mbit/s) there is plenty of margin; at High Speed (480 Mbit/s) there is not: matched lengths, unbroken ground plane under the pair, no unnecessary vias.

The ID pin only exists on Mini and Micro. A plain device leaves it unconnected. An OTG device reads it to pick its role: grounded, it becomes the host.

The shield is not ground. The connector’s metal shell goes to chassis ground, often through an RC network or a ferrite, not straight to the board’s digital ground. That choice weighs heavily on ESD immunity and radiated emissions.

Charging without enumeration. A dedicated charger (DCP in the USB Battery Charging 1.2 specification) shorts D+ to D−. Without enumeration, USB 2.0 only allows 100 mA (500 mA once configured): a device that wants more without enumerating has to detect that short.

Frequently asked questions

FAQ

Which pin is +5 V on a USB connector?: Pin 1 (VBUS) on every pre-USB-C connector: Type-A, Type-B, Mini-B, Micro-B and their USB 3 versions. Ground is pin 4 on A and B, pin 5 on Mini and Micro.
What are the wire colors in a USB cable?: In a standard USB 2.0 cable: red for VBUS, white for D−, green for D+, black for ground. Cheap cables do not always follow the code, so check with a multimeter before soldering.
What is the Micro-USB ID pin for?: It sets the role in USB On-The-Go. An OTG cable ties ID to ground at the A plug end: the device that receives it switches to host mode and powers the peripheral. Floating, the device stays a peripheral.
Does a USB 2.0 cable work in a USB 3 port?: Yes. USB 3 Standard-A, Standard-B and Micro-B receptacles accept the matching USB 2.0 plugs, and the link simply falls back to USB 2.0. The reverse fails for Type-B: the taller USB 3 Standard-B plug does not fit a USB 2.0 B receptacle.

Sources

Tables built from these documents and cross-checked against manufacturer datasheets. Always check the datasheet of the connector you actually use: some manufacturers number differently.