# USB 3 Standard-A plug

> a legacy USB plug that preceded USB-C (“A” indicating the host end)

**Wikidata**: [Q133459079](https://www.wikidata.org/wiki/Q133459079)  
**Source**: https://4ort.xyz/entity/usb-3-standard-a-plug

## Summary
The USB 3 Standard-A plug is a legacy USB connector designed for the host end of a cable connection, officially designated as the USB 3.1 Standard-A plug. It preceded the modern USB-C standard and is characterized by its compatibility with USB 2.0 ports and a 9-pin configuration that supports SuperSpeed data transfer. It connects to both USB 3 and USB 2 Standard-A receptacles.

## Key Facts
*   **Official Name:** USB 3.1 Standard-A plug.
*   **Predecessor Status:** Classified as a legacy plug that preceded the USB-C plug.
*   **Function:** Serves as the "A" or host end of a connection (distinct from device ends like Standard-B).
*   **Pin Configuration:** Features a 9-pin layout; the first 4 pins (VBUS, D−, D+, GND) are backward compatible with USB 2.0, while pins 5–9 (SSRX−, SSRX+, GND_DRAIN, SSTX−, SSTX+) handle SuperSpeed signals.
*   **Voltage:** Operates with a VBUS voltage of 5 Volts.
*   **Backward Compatibility:** Physically connects with USB 2 Standard-A receptacles in addition to USB 3 Standard-A receptacles.
*   **Visual Identification:** Standard wire colors for pins include Red (VBUS), White (D−), Green (D+), and Black (GND).
*   **Aliases:** Also known as the USB SuperSpeed+ Standard-A plug, USB 3.0 Standard-A plug, and Standard USB 3 Type-A plug.

## FAQs
### Q: Is the USB 3 Standard-A plug compatible with older USB ports?
A: Yes, the plug is designed to connect with USB 2 Standard-A receptacles. It retains the legacy 4-pin configuration (VBUS, D-, D+, GND) at the front of the connector to ensure backward compatibility.

### Q: How does the USB 3 Standard-A plug differ from a USB-C plug?
A: The USB 3 Standard-A plug is a legacy connector that preceded USB-C. Unlike the reversible USB-C plug, the Standard-A plug has a distinct rectangular shape that must be inserted in a specific orientation.

### Q: What are the extra pins in the USB 3 Standard-A plug used for?
A: Beyond the standard power and data pins, this plug includes five additional pins (SSRX−, SSRX+, GND_DRAIN, SSTX−, SSTX+) located further back in the connector. These pins enable SuperSpeed data transmission.

## Why It Matters
The USB 3 Standard-A plug represents a critical evolutionary step in wired connectivity, bridging the gap between the ubiquitous USB 2.0 standard and the modern USB-C era. Its primary significance lies in its ability to introduce high-speed "SuperSpeed" data transfer (via the extra 5 pins) while maintaining the physical backward compatibility that made the USB Standard-A interface the industry standard for host controllers.

By allowing users to plug a new USB 3.0 device into an existing computer without requiring new hardware for basic functionality, this connector design facilitated a smooth transition for the ecosystem. It extended the lifespan of the rectangular "Type-A" port found on billions of computers and chargers worldwide before the industry eventually shifted toward the reversible, multi-functional USB-C plug.

## Notable For
*   **Host-Side Identification:** It is explicitly the "host end" plug, distinguishing it from "B" or "Micro" connectors found on peripheral devices.
*   **Hybrid Pin Architecture:** It uniquely stacks 5 new high-speed pins behind the 4 legacy USB 2.0 pins, allowing a single connector to serve two different protocol generations simultaneously.
*   **Legacy Status:** It is the final revision of the original rectangular USB plug design before the standard transitioned to the symmetrical USB-C form factor.
*   **Nomenclature Complexity:** It is known by multiple aliases, including USB 3.0, USB 3.1, SuperSpeed, and SuperSpeed+, reflecting the evolving marketing names of the USB specification over time.

## Body

### Technical Specifications (Pinout)
The USB 3 Standard-A plug features a 9-pin design that expands upon the original 4-pin USB architecture.

**Legacy Pins (USB 2.0 Compatible):**
*   **Pin 1 (VBUS):** Red wire; IC power-supply pin; 5 Volts.
*   **Pin 2 (D−):** White wire; Data minus.
*   **Pin 3 (D+):** Green wire; Data plus.
*   **Pin 4 (GND):** Black wire; Ground.

**SuperSpeed Pins (USB 3.x Added):**
*   **Pin 5 (SSRX−):** SuperSpeed Receive minus.
*   **Pin 6 (SSRX+):** SuperSpeed Receive plus.
*   **Pin 7 (GND_DRAIN):** Ground drain for signal integrity.
*   **Pin 8 (SSTX−):** SuperSpeed Transmit minus.
*   **Pin 9 (SSTX+):** SuperSpeed Transmit plus.

### Classification and Relationships
The USB 3 Standard-A plug is an instance of the "USB 3 Standard-A connector" class and the "USB Standard-A plug" class. It serves as the logical opposite to the **USB 3 Standard-A receptacle** (the port on a device). While it is physically distinct from the **USB 3 Standard-B plug** and **USB 3 Micro-A plug**, it shares the same generation of technology. It has been officially replaced in new designs by the **USB-C plug**, though it remains in wide use as a legacy port.

### Naming and Aliases
Official documentation refers to this entity as the **USB 3.1 Standard-A plug**. However, it is widely referenced by several names in technical and consumer contexts, including:
*   USB SuperSpeed+ Standard-A plug
*   USB SS+ Standard-A plug
*   USB SuperSpeed Standard-A plug
*   USB 3.0 Standard-A plug
*   Standard USB 3 Type-A plug

## References

1. [Source](https://www.usb.org/document-library/usb-31-legacy-cable-and-connector-revision-10)
2. [Source](https://www.usb.org/document-library/universal-serial-bus-31-legacy-connectors-and-cable-assemblies-compliance-document)
3. [Source](https://www.usb.org/document-library/usb-32-revision-11-june-2022)
4. [Source](https://www.usb.org/document-library/usb-type-cr-connectors-and-cable-assemblies-compliance-document-rev-21b)
5. [Source](https://www.usb.org/document-library/usb-type-cr-cable-and-connector-specification-release-24)
6. [Source](https://www.usb.org/document-library/usb-20-specification)