# USB Micro plug > a class of legacy USB plugs that preceded USB-C, along with Standard and Mini **Wikidata**: [Q133871421](https://www.wikidata.org/wiki/Q133871421) **Source**: https://4ort.xyz/entity/usb-micro-plug ## Summary A USB Micro plug is a class of legacy USB connectors that served as predecessors to the modern USB-C standard. It is categorized alongside Standard and Mini plugs as a distinct type of legacy USB interface, primarily used for connecting peripheral devices and hosts before the widespread adoption of USB-C. ## Key Facts - **Classification:** A subclass of both "Micro-USB" and "legacy USB plug" (a category encompassing all USB plugs other than Type-C). - **Succession:** Preceded the USB-C plug, which acts as the replacement for all legacy USB plug types. - **Predecessor:** Replaced the USB Mini plug. - **Aliases:** Also known as "Micro-USB plug." - **Variants:** Includes distinct classes for hosts (USB Micro-A plug) and peripheral devices (USB Micro-B plug). - **Generations:** Divided into "USB 2 Micro plug" (carrying USB 1–2 and power) and "USB 3 Micro plug." - **Differentiation:** Distinct from the USB Standard plug, USB Mini plug, USB-C plug, and the USB Micro receptacle. ## FAQs ### Q: What is the USB Micro plug? A: The USB Micro plug is a class of legacy USB connectors that were utilized before the introduction of USB-C. It belongs to the Micro-USB family and is distinct from Standard and Mini USB plugs. ### Q: What is the difference between USB Micro-A and USB Micro-B plugs? A: According to the source hierarchy, the USB Micro-A plug is designed for the host end of connections, whereas the USB Micro-B plug is designed for the peripheral device end. ### Q: Did the USB Micro plug replace older connectors? A: Yes, the USB Micro plug class replaced the USB Mini plug. It has subsequently been replaced by the USB-C plug. ## Why It Matters The USB Micro plug represents a significant phase in the evolution of connectivity standards, serving as the dominant legacy interface before the industry transitioned to the unified USB-C standard. As a class, it introduced specific distinctions between host (Micro-A) and peripheral (Micro-B) connections, as well as advancements in data transfer capabilities seen in the shift from USB 2 to USB 3 versions. Its relevance lies in its status as the immediate predecessor to the modern reversible USB-C plug. Understanding the USB Micro plug is essential for identifying and managing legacy hardware, as it encompasses the specific connector types (Micro-A and Micro-B) that were universal on mobile devices and peripherals prior to the USB-C transition. The existence of separate classes for USB 2 and USB 3 versions within this plug type also highlights the technical stratification of speed and power delivery that existed before the consolidation offered by the USB-C standard. ## Notable For - Being the immediate legacy class of plugs preceding the universal USB-C standard. - Encompassing specific sub-types for different functions, including "USB Micro-A plug" (host) and "USB Micro-B plug" (peripheral). - Including distinct classes for different data generations, specifically the USB 2 Micro plug and the USB 3 Micro plug. - Replacing the older USB Mini plug standard while eventually being subsumed by USB-C. - Being officially designated as part of the "legacy USB plug" category, which covers all non-Type-C connectors. ## Body ### Definition and Hierarchy The **USB Micro plug** is a class of legacy USB connectors. It is taxonomically defined as a subclass of **Micro-USB** and **legacy USB plug**. The term "legacy USB plug" specifically refers to the class of all USB plugs other than Type-C (USB-C), which has been introduced to replace all previous form factors. ### Historical Context This connector class is part of the progression of USB technology. It followed the **USB Mini plug**, which it eventually replaced. Subsequently, the USB Micro plug and all other legacy types have been succeeded by the **USB-C plug**. Specifically, the USB 2 Micro plug was replaced by the USB 2 Type-C plug. ### Variants and Specifications The USB Micro plug class includes several specific variants defined by their function and generation: * **USB Micro-A plug:** A legacy class designed for the host end of connections. * **USB Micro-B plug:** A legacy class designed for the peripheral device end. * **USB 2 Micro plug:** A class capable of carrying USB 1–2 signals and power. * **USB 3 Micro plug:** A later class of legacy Micro plugs offering higher data rates. Visual documentation of these legacy plugs often groups USB 3 and USB 2 versions of both Micro-A and Micro-B plugs together to illustrate their scale and structure. ### Official Nomenclature The official name for this entity is "USB Micro plug," as referenced in USB-IF documentation including the "USB 3.1 Legacy Cable and Connector" and "USB 3.2" revision documents. It is alternatively referred to as the "Micro-USB plug." It is distinct from the receptacle (the port on the device) and other form factors like the Standard or Mini 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)