# USB Type-B plug

> a class of legacy USB plugs that preceded USB-C (“B” indicating the peripheral device end, all other pre-C plugs being Type-A)

**Wikidata**: [Q133871518](https://www.wikidata.org/wiki/Q133871518)  
**Source**: https://4ort.xyz/entity/usb-type-b-plug

## Summary
The USB Type-B plug is a class of legacy USB plugs designed to connect to the peripheral device end of a cable, distinguishing it from the host-side Type-A plugs. This classification encompasses various form factors, including Standard-B, Mini-B, and Micro-B, which preceded the modern USB Type-C standard. These plugs have been effectively replaced by the USB Type-C plug.

## Key Facts
- **Classification:** The USB Type-B plug is a subclass of the "legacy USB plug" category, covering all USB plugs that preceded USB-C.
- **Function:** The "B" designation indicates the plug is intended for the peripheral device end of a cable, whereas pre-C host connections utilize Type-A plugs.
- **Replaced By:** The entire class of USB Type-B plugs has been replaced by the USB Type-C plug.
- **Variants:** Specific subclasses include the USB Standard-B plug, USB Micro-B plug, USB Mini-B plug, USB 2 Type-B plug, and USB 3 Type-B plug.
- **Distinctions:** It is structurally and functionally different from the USB Type-B receptacle (the port), the USB Type-A plug, and the USB Type-C plug.
- **Evolution:** The USB Mini-B plug, the oldest compact version, was replaced by the USB Micro-B plug, which was subsequently replaced by the USB 2 Type-C plug.

## FAQs
### Q: What is the main function of a USB Type-B plug?
A: The USB Type-B plug serves as the connector at the peripheral device end of a USB cable. It is distinct from Type-A plugs, which connect to the host device (such as a computer).

### Q: Is the USB Type-B plug still used in modern devices?
A: The USB Type-B plug is considered a legacy connector class. It has been replaced by the USB Type-C plug, which is now the standard for both hosts and peripheral devices.

### Q: What is the difference between USB Type-B and USB Type-A?
A: In pre-USB-C environments, Type-A plugs were used for the host end (upstream) of the connection, while Type-B plugs were used for the peripheral end (downstream).

### Q: What are the different types of USB Type-B plugs?
A: The class includes several variants such as Standard-B (often used for printers), Mini-B (used in older compact electronics), Micro-B (used in older smartphones), and specific USB 2 and USB 3 versions.

## Why It Matters
The USB Type-B plug represents a critical era in the history of universal connectivity, defining the "device" side of the USB connection standard for over two decades. Before the advent of the reversible, universal USB Type-C, USB architecture relied on a strict division of labor: Type-A for hosts (computers, chargers) and Type-B for peripherals (printers, external drives, cameras). This classification system ensured that users could distinguish between the upstream and downstream flow of data and power.

While these plugs are now categorized as "legacy," understanding the Type-B family is essential for maintaining older hardware and understanding the evolution of connector technology. The progression from the bulky Standard-B to the Mini-B and finally the Micro-B illustrates the industry's drive toward miniaturization before finally consolidating all functions into the USB Type-C standard. The Type-B plug's role as the dedicated peripheral connector solved the cabling confusion of pre-USB proprietary ports, standardizing how accessories connected to computers.

## Notable For
- **Defining the Peripheral End:** It is specifically distinguished as the connector class for the peripheral device end of cables, separate from the host-side Type-A.
- **Preceding USB-C:** It constitutes the collective class of plugs that existed prior to the introduction of the unified USB-C standard.
- **Variety of Form Factors:** It encompasses a wide range of shapes and sizes, from the square Standard-B to the flat Micro-B, accommodating various device thickness requirements over time.
- **Evolutionary Hierarchy:** It includes the USB Mini-B, noted as the oldest compact legacy plug, which highlights the rapid iteration of connector designs in the 2000s.

## Body
### Definition and Context
The USB Type-B plug is a class of legacy USB connectors. The defining characteristic of this class is its location at the "peripheral device end" of a cable. In the USB topology that existed before USB-C, cables were asymmetrical: the host (computer) used a Type-A plug, while the peripheral (device) used a Type-B plug.

### Hierarchy and Classification
This entity is a subclass of the broader "USB Type-B connector" and "legacy USB plug" classes. The term "legacy" is applied because these connectors preceded the USB-C standard, which replaces all previous USB plug types.

The class includes several distinct subclasses based on size and USB generation:
- **USB Standard-B plug:** The original larger design, typically used for stationary peripherals.
- **USB Mini-B plug:** The oldest compact legacy plug, designed for portable devices.
- **USB Micro-B plug:** A slimmer successor to the Mini-B, widely used in mobile devices before USB-C.
- **USB 2 Type-B plug:** Variants carrying only USB 1–2 signals and power.
- **USB 3 Type-B plug:** Updated variants designed to handle higher data transfer speeds.

### Relationships and Replacements
The USB Type-B plug is structurally distinct from the USB Type-B receptacle (the female port on the device) and the USB Type-A plug.

The evolutionary chain for the compact versions of these plugs is clearly defined:
1.  **USB Mini-B plug:** Replaced by the USB Micro-B plug.
2.  **USB Micro-B plug:** Later replaced by the USB 2 Type-C plug.

Ultimately, the entire class of USB Type-B plugs has been replaced by the **USB Type-C plug**, which serves as a universal connector for both hosts and peripherals.

### Visual Identification
Visual representations of the USB Type-B plug class often display a grouping of these legacy connectors to scale. Illustrations typically identify the "USB Powered-B plug," "USB 3 Standard-B plug," "USB 3 Micro-B plug," "USB 2 Standard-B plug," "USB 2 Micro-B plug," and "USB Mini-B plug" collectively as "The USB Type-B plugs."