USB stands for Universal Serial Bus, a shared standard for the plugs, ports and cables that connect devices to computers and chargers. A mouse, a keyboard, a printer, a flash drive and a phone charger can all use it, and that wide reach is what "universal" promises.
Before it caught on, a desktop computer had a different port for nearly every gadget: one shape for the printer, another for the mouse, another for the modem. A group of computer and electronics companies designed USB in the mid 1990s to replace that tangle with one kind of connection that could also supply power.
Quick facts
Stands for
Universal Serial BusType
Initialism, said "U S B"What it does
Carries data and power between devicesCommon plugs
USB-A, USB-B, Micro USB, USB-CSeen on
Laptops, chargers, cars, TVs, game consolesRelated terms
What does USB stand for? Breaking down the three words
| Letter | Word | What it means here |
|---|---|---|
| U | Universal | One standard meant for almost any device |
| S | Serial | Data travels one bit after another along a wire |
| B | Bus | A shared pathway that several devices can use |
"Bus" is an old computer word for a channel that moves data between parts. It has nothing to do with a vehicle, though the idea of many riders sharing one route is a handy picture. People say each letter, "you ess bee," so the usb acronym is really an initialism. If the labels confuse you, acronym vs abbreviation untangles them.
USB plug shapes you will run into
- USB-A: the flat rectangle that only fits one way up. Found on older laptops, desktops and wall chargers.
- USB-B: a squarer plug, mostly on printers and some music gear.
- Mini USB and Micro USB: small plugs used on older phones, cameras and handheld devices.
- USB-C: the small oval plug that fits either way up. It now appears on most new phones, tablets and laptops.
Box label: "Includes USB-C to USB-A cable." One end fits a new phone, and the other end fits an older rectangular charger or computer port.
Version numbers and speed
The plug shape and the version number are two separate things. The shape tells you what fits. The version tells you how fast data can move. USB 2.0 tops out at 480 megabits per second, while USB 3.0 raised that to 5 gigabits per second, and later versions go higher still. Speeds are often listed in Mbps or Gbps.
A USB-C plug can be wired for slow or fast data, so two cables that look the same may behave very differently. If a file copy feels slow, the cable or the port version may be the reason.
How people use the term in daily life
In speech, "a USB" often means a small flash drive. A teacher might say "save your project to a USB," and everyone knows she means a thumb drive. Other everyday phrases:
- "Plug it into a USB port" means the slot on a computer, TV or car.
- "A USB charger" is a wall block with a USB socket.
- "USB powered" means the device runs on power from the cable, like a desk fan or a reading light.
Hotel room card: "USB outlets are on the lamp base." You can charge a phone there with just your cable, no wall plug needed.
USB stands for one standard, not one cable
Because so many things say USB, people sometimes think every USB cable works the same. Some only charge and do not carry data. Some carry video to a monitor, and some do not. Fast charging also depends on the charger and the device agreeing on how much power to send.
A few quick tips help:
- Keep the cable that came with a device for that device.
- Look for the speed or power rating printed on the box.
- Do not plug in a found flash drive, since it can carry harmful files.
- Use "a" before it in writing, since it starts with a "you" sound: "a USB cable."
Look-alike tech terms
USB often sits next to other port names on a laptop spec sheet. HDMI carries video and sound to a TV or monitor. An SSD is a solid state drive, and portable ones usually connect by USB. A LAN port is the wired network jack. Browse more on the tech acronyms hub.
Questions people ask
What does USB stand for on a phone charger?
It still stands for Universal Serial Bus. On a charger, it tells you the block has a USB socket, so any matching USB cable can plug into it.
Is USB-C the same as USB 3?
No. USB-C is the shape of the plug, while USB 3 is a speed version. A USB-C port can run at many different speeds.
What is the full form of USB in computer terms?
The usb full form is Universal Serial Bus. It names the standard for how devices connect, share data and draw power.
Why do people call a flash drive a USB?
A flash drive plugs into a USB port, so people shortened "USB flash drive" to just "USB." It is casual but widely understood.
Do you say a USB or an USB?
Say "a USB," because the first letter is pronounced "you," which starts with a consonant sound.