EMZETT.USB-B
In short: A square USB connector type traditionally used on the device side (rather than the PC) — classically, for example, on printers.
In more detail: USB-B cables usually have USB-A on the PC side and USB-B (or a Mini/Micro variant) on the device side. With the spread of USB-C, USB-B is also becoming increasingly rare.
In Depth
Why there were two connector shapes at all
The basic idea behind the asymmetric USB system was originally to deliberately design PC-side (“host”) and device-side (“device”) connectors differently, so users don’t accidentally connect two PCs or two peripherals directly to each other — a misconfiguration that could easily happen with symmetrical connectors and, depending on the electrical design, could even damage hardware. USB-A was intended for the host side (PC, charger, hub), USB-B for the device side (printer, scanner, external drive). The classic, square USB-B connector (officially “Type B Standard”) with its characteristic, slightly bevelled top edge is still found today mainly on printers, some external hard drive enclosures, MIDI devices and lab instruments.
The Mini and Micro generations
For smaller, mobile devices, the bulky standard-B connector was impractical, which is why USB-B was supplemented over time by more compact variants. Mini-USB (mid-2000s) was mainly used on early MP3 players, digital cameras and first-generation smartphones, but turned out to be mechanically not very robust — the connector wore out relatively quickly with frequent plugging and unplugging. Micro-USB replaced Mini-USB and became the de-facto standard for Android smartphones for years, before USB-C took over that role from around 2015. The EU-wide charger unification initially relied on Micro-USB, before the standard was fully switched to USB-C in 2024.
Functional limits compared to USB-C
All USB-B variants (Standard, Mini, Micro) transmit only the classic USB protocol at the older speed levels — the connector shape itself considerably limits the maximum possible data rate and power delivery compared to USB-C. Modern capabilities like high Power Delivery output (up to 240 watts with USB-C), DisplayPort video output over the same connector (Alternate Mode), or Thunderbolt compatibility simply don’t exist for USB-B shapes — these features were only introduced with the USB-C specification and need the additional contact pins and the symmetrical, reversible connector shape of USB-C.
Practical relevance today
Anyone still running USB-B devices today (typically older printers or long-lived lab hardware) usually needs a USB-A-to-USB-B cable, since modern laptops increasingly only have USB-C ports — a USB-C-to-USB-A adapter or a correspondingly switchable cable helps here.