# USB 3 Micro-B receptacle > a legacy USB receptacle that preceded USB-C (“B” indicating the peripheral device end) **Wikidata**: [Q133458748](https://www.wikidata.org/wiki/Q133458748) **Source**: https://4ort.xyz/entity/usb-3-micro-b-receptacle ## Summary The USB 3 Micro-B receptacle is a legacy peripheral-side USB connector that preceded USB-C, supporting faster data transfer rates up to 5–10 Gbps. It was commonly used in devices such as external hard drives, smartphones, and tablets before being superseded by USB-C. The “B” designation indicates its role as the peripheral device end of the connection. ## Key Facts - Official name: USB 3.1 Micro-B receptacle (as per USB 3.1 Legacy Cable and Connector Revision 1.0). - Pin count: 10 pins, including VBUS, D−, D+, ID, GND, SSTX−, SSTX+, GND_DRAIN, SSRX−, SSRX+. - Supports data speeds up to 5 Gbps (USB 3.0) or 10 Gbps (USB 3.1 SuperSpeed+). - Replaced by: USB-C receptacle. - Connects with: USB 3 Micro-B plug, USB 2 Micro-B plug. - Aliases: SuperSpeed Micro-B, USB 3.0 Micro-B, Micro-USB 3.1 Type-B receptacle. - Part of classes: USB 3 Micro-B connector, USB 3 Type-B receptacle, USB Micro-B receptacle. - Opposite of: USB 3 Micro-B plug. - Image reference: [Wikimedia Commons](https://commons.wikimedia.org/wiki/Special:FilePath/USB_connector_illustration,_to_scale,_front_view,_legacy,_USB_3_Micro-B_receptacle.svg). ## FAQs ### Q: What devices use a USB 3 Micro-B receptacle? A: Devices like external storage drives, smartphones, tablets, and cameras used this connector for high-speed data transfer and charging. It was especially common in Android-based peripherals prior to USB-C adoption. ### Q: Is USB 3 Micro-B the same as USB-C? A: No. USB 3 Micro-B is an older, physically distinct connector with a specific orientation and pin layout. USB-C is newer, reversible, and supports higher speeds and more protocols. ### Q: Can I plug a USB 2 cable into a USB 3 Micro-B receptacle? A: Yes. USB 3 Micro-B receptacles are backward compatible with USB 2 Micro-B plugs, though data speeds will be limited to USB 2.0 rates. ## Why It Matters The USB 3 Micro-B receptacle played a key transitional role in the evolution of USB technology, bridging the gap between USB 2.0 speeds and the modern era of high-bandwidth connectivity. As one of the first widely adopted connectors to support SuperSpeed data transfer (up to 5 Gbps), it enabled faster file transfers and improved performance in portable electronics. Though now largely replaced by USB-C, it remains relevant in legacy systems and provides insight into how USB standards evolved toward universal, reversible designs. Its structured pinout and compatibility features also reflect the engineering considerations behind scalable interface design. ## Notable For - First widely adopted Micro-B connector to support USB 3.0 SuperSpeed data rates. - Backward-compatible with USB 2.0 Micro-B plugs. - Physically distinct from earlier USB Micro-B connectors due to additional pins and required black insulator color. - Featured in early generations of high-performance mobile and peripheral devices. - Marked the final major iteration of non-reversible USB connectors before USB-C. ## Body ### Technical Overview The USB 3 Micro-B receptacle is a 10-pin interface designed for use on peripheral devices. It supports both legacy USB 2.0 signaling and USB 3.0/3.1 SuperSpeed data transmission. The connector includes dedicated pins for power (VBUS), ground (GND), differential data lines (D+, D−), and new high-speed signal pairs (SSTX±, SSRX±). ### Pin Configuration | Pin | Signal | Color (if applicable) | Function | |-----|------------|------------------------|-----------------------------------| | 1 | VBUS | Red | Power supply (+5V) | | 2 | D− | White | USB 2.0 data line | | 3 | D+ | Green | USB 2.0 data line | | 4 | ID | — | USB On-The-Go detection | | 5 | GND | Black | Ground | | 6 | SSTX− | — | SuperSpeed transmit negative | | 7 | SSTX+ | — | SuperSpeed transmit positive | | 8 | GND_DRAIN | — | Drain wire/packaging ground | | 9 | SSRX− | — | SuperSpeed receive negative | | 10 | SSRX+ | — | SuperSpeed receive positive | ### Standards & Specifications - Defined under the **USB 3.1 Legacy Cable and Connector Revision 1.0** specification. - Referenced in compliance documents including the **USB 3.2 Revision 1.1**. - Supports dual-role operation via the **ID pin**, enabling **USB On-The-Go (OTG)** functionality. - Required black insulator color distinguishes it visually from earlier USB 2.0 Micro-B connectors. ### Compatibility - Compatible with **USB 3 Micro-B plugs** and **USB 2 Micro-B plugs**. - Not interchangeable with **USB 3 Micro-AB**, **USB 3 Standard-B**, or **USB 2 Micro-B** receptacles. - Fully backward compatible with existing USB software stacks and drivers. ### Historical Context - Introduced alongside the broader rollout of **USB 3.0** in late 2000s and standardized further in **USB 3.1**. - Widely implemented in consumer electronics until around **2015–2018**, when **USB-C** began widespread adoption. - Represents the last generation of non-symmetrical USB connectors before the shift to fully reversible designs. ## 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)