# USB Standard-A connector > Class of full-size legacy USB connectors (host end) that preceded USB-C **Wikidata**: [Q133871018](https://www.wikidata.org/wiki/Q133871018) **Source**: https://4ort.xyz/entity/usb-standard-a-connector ## Summary The **USB Standard‑A connector** is the full‑size, host‑side USB connector that was used on most computers and peripherals before the introduction of USB‑C. It belongs to the legacy USB Standard family and is commonly called a “USB‑A” or “Standard‑A” connector. ## Key Facts - **Class definition** – It is a class of full‑size legacy USB connectors (host end) that preceded USB‑C【wikidata】. - **Parent classes** – Subclass of both **USB Standard connector** and **USB Type‑A connector**【wikidata】. - **Official name** – “USB Standard‑A connector,” as defined in the USB 3.1 legacy cable and connector specification (revision 10) and the USB 3.2 revision (June 2022)【wikidata】. - **Variants** – Includes **USB 2 Standard‑A** and **USB 3 Standard‑A** connectors, each with corresponding plugs and receptacles【wikidata】. - **Aliases** – Also known as **Standard USB‑A connector**【wikidata】. - **Different from** – Not to be confused with USB Standard‑B connector, USB Micro‑A plug, or USB Mini‑A connector【wikidata】. - **Image reference** – Illustrated in a scale diagram showing USB 3 and USB 2 Standard‑A plugs and receptacles【wikidata】. - **Commons category** – Listed under **USB Standard‑A connectors** on Wikimedia Commons【wikidata】. - **Sitelink count** – One Wikipedia/Commons sitelink is associated with the entry【wikidata】. ## FAQs ### Q: What devices typically used a USB Standard‑A connector? A: Most desktop PCs, laptops, chargers, and peripheral devices (e.g., keyboards, mice, flash drives) used a USB Standard‑A port for the host side before USB‑C became common. ### Q: How does USB Standard‑A differ from USB‑C? A: USB Standard‑A is a rectangular, one‑way connector used only on the host side, whereas USB‑C is a reversible, symmetrical connector that supports both host and device roles and higher data/power rates. ### Q: Are USB 2 and USB 3 Standard‑A connectors interchangeable? A: Physically they share the same shape, but USB 3 Standard‑A adds extra pins for higher‑speed data; a USB 3 port can accept a USB 2 plug, but a USB 2 port cannot use a USB 3 plug’s extra pins. ## Why It Matters The USB Standard‑A connector defined the first universal, mass‑market interface for connecting computers to a wide range of peripherals. By providing a single, standardized host‑side port, it eliminated the need for multiple proprietary connectors, simplifying hardware design and user experience. Its durability and ease of use helped drive the rapid adoption of USB technology worldwide, enabling reliable power delivery and data transfer for billions of devices over two decades. Although newer connectors like USB‑C now dominate, the Standard‑A form factor remains prevalent in legacy equipment, ensuring backward compatibility and protecting investments in existing hardware ecosystems. Understanding its role clarifies the evolution of USB standards and informs decisions about device compatibility, cable selection, and transition planning for modern systems. ## Notable For - **Legacy status** – The primary host‑side connector for USB 1.x, 2.0, and early 3.x devices before USB‑C. - **Broad adoption** – Became the de‑facto standard for consumer and enterprise hardware worldwide. - **Physical simplicity** – A rectangular, non‑reversible design that made insertion direction obvious. - **Compatibility layers** – USB 3 Standard‑A ports accept USB 2 plugs, preserving interoperability across generations. - **Distinct classification** – Clearly separated from USB Standard‑B, Micro‑A, and Mini‑A families, avoiding connector confusion. ## Body ### Definition and Classification - The USB Standard‑A connector is defined as a **full‑size, host‑end** USB interface. - It is part of the **USB Type‑A connector** class and the broader **USB Standard connector** family. ### Variants #### USB 2 Standard‑A - Supports up to **480 Mbps** (High‑Speed) data rates. - Uses four pins (Vbus, D‑, D+, GND). #### USB 3 Standard‑A - Adds **five additional pins** for SuperSpeed data (up to **5 Gbps** in USB 3.0, higher in later revisions). - Physically compatible with USB 2 plugs; the extra pins are ignored by USB 2 devices. ### Physical Characteristics - Rectangular shape, typically **12 mm × 4.5 mm** (standard dimensions for legacy USB‑A). - Non‑reversible; the plug can be inserted only one way. ### Compatibility and Interoperability - **Backward compatible**: USB 3 Standard‑A ports accept USB 2 Standard‑A plugs. - **Forward compatibility**: USB 2 devices work in USB 3 ports, but operate at USB 2 speeds. ### Legacy Role and Transition - Served as the default host connector from the introduction of USB 1.0 (1996) through the early adoption of USB‑C (late 2010s). - Remains in widespread use on older equipment, power adapters, and many consumer devices, ensuring continued relevance despite newer connector standards. ### Documentation and Standards References - Officially named in the **USB 3.1 Legacy Cable and Connector Revision 10** (2025‑05‑10) and the **USB 3.2 Revision 11** (June 2022) documents from the USB Implementers Forum. --- *All statements are derived from the provided source material and referenced Wikidata entries.* ## 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)