# USB 2 Micro-B plug > a legacy USB plug that preceded USB-C (“B” indicating the peripheral device end) **Wikidata**: [Q102144886](https://www.wikidata.org/wiki/Q102144886) **Source**: https://4ort.xyz/entity/usb-2-micro-b-plug ## Summary The USB 2 Micro-B plug is a legacy USB connector located at the peripheral device end of cables, designed to carry USB 1–2 data and power. Distinguished by its required black insulator color, it served as the most compact connector in the USB 2 legacy family before being replaced by the USB-C plug. It replaced the larger USB Mini-B plug and is mechanically compatible with various Micro-AB and Micro-B receptacles. ## Key Facts * **Official Name:** USB 2.0 Micro-B plug * **Classification:** Instance of USB 2 Micro-B connector, USB Micro-B plug, and USB 2 Type-B plug. * **Succession:** Replaced the USB Mini-B plug and was subsequently replaced by the USB-C plug. * **Pin Configuration:** Features 5 pins (VBUS, D−, D+, ID, GND) and contains 10 leads. * **ID Pin Function:** Pin 4 (ID) is dedicated to USB On-The-Go functionality. * **Visual Identifier:** Requires a black insulator color to distinguish it from other USB types. * **Compatibility:** Connects with USB 2 Micro-AB/B receptacles and USB 3 Micro-AB/B receptacles. * **Wire Coding:** VBUS (Red, Pin 1), D− (White, Pin 2), D+ (Green, Pin 3), GND (Black, Pin 5). ## FAQs ### Q: What is the difference between the USB 2 Micro-B plug and the USB Mini-B plug? A: The USB 2 Micro-B plug is the successor to the USB Mini-B plug. It was designed to be a more compact legacy connector for peripheral devices. ### Q: Can a USB 2 Micro-B plug fit into a USB 3 Micro-B receptacle? A: Yes, the USB 2 Micro-B plug is listed as connecting with USB 3 Micro-AB and USB 3 Micro-B receptacles, in addition to its native USB 2 receptacles. ### Q: What does the "B" in USB 2 Micro-B plug indicate? A: The "B" indicates that the plug is designed for the peripheral device end of a cable, as opposed to the host (A) end. ### Q: What is the function of the ID pin in this connector? A: The ID pin (Pin 4) is included specifically to support USB On-The-Go (OTG) functionality, which allows devices to act as either a host or a peripheral. ## Why It Matters The USB 2 Micro-B plug represents a critical evolutionary step in the standardization of mobile and peripheral connectivity. Before the widespread adoption of USB-C, the Micro-B plug became the ubiquitous charging and data port for billions of smartphones, tablets, and portable electronics. Its design focused on durability and compactness compared to the preceding Mini-B standard, enabling manufacturers to create thinner devices. The connector's specific inclusion of an ID pin for USB On-The-Go also marked a shift in usability, allowing portable devices to communicate directly with each other without a PC host. While it is now considered a "legacy" connector replaced by the reversible USB-C plug, the USB 2 Micro-B remains relevant in the transition of technology, serving as the standard interface for many peripherals, industrial equipment, and older electronics still in use today. Its 5-pin layout (carrying VBUS, D−, D+, ID, and GND) defined the electrical and mechanical constraints of mobile connectivity for nearly a decade. ## Notable For * **Most Compact Legacy Plug:** Defined as the most compact legacy USB 2 connector class at the peripheral device end. * **Standard Color Coding:** Notable for mandating a black insulator color, which serves as a quick visual identifier for technicians and users. * **Transition to OTG:** One of the first standard mobile plugs to integrate an ID pin specifically for USB On-The-Go protocols. * **Ubiquity:** Served as the de facto standard for mobile phone charging and data transfer prior to the USB-C era. ## Body ### Technical Specifications The USB 2 Micro-B plug is defined by a specific set of mechanical and electrical characteristics detailed in USB legacy specifications. It features a 5-pin interface arranged to carry power and high-speed data. **Pinout and Wiring:** The connector utilizes a 5-pin layout with standardized wire colors: * **Pin 1 (VBUS):** Red wire; functions as the IC power-supply pin. * **Pin 2 (D−):** White wire; data negative. * **Pin 3 (D+):** Green wire; data positive. * **Pin 4 (ID):** No color specified; utilized for USB On-The-Go identification. * **Pin 5 (GND):** Black wire; functions as the ground. The plug assembly contains **10 leads**. ### Classification and Relationships The USB 2 Micro-B plug is an instance of multiple connector classes, including the **USB 2 Micro-B connector**, **USB 2 Micro plug**, and **USB 2 Type-B plug**. It is strictly differentiated from the **USB 2 Micro-B receptacle** (the port it plugs into) and the **USB 2 Micro-A plug**. ### Historical Context This connector is classified as a "legacy" technology. It was engineered to be smaller than the **USB Mini-B plug**, which it replaced. Eventually, the industry transitioned away from the USB 2 Micro-B form factor in favor of the reversible and more versatile **USB-C plug**. Despite being superseded, official documentation reaffirms its specifications as late as 2022 in USB 3.2 legacy connector revisions. ## 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)