A USB pen drive, also called flash drive, memory stick or USB-Stick is drive and media in one. A typical pen drive is a flash memory data storage device integrated with a USB (universal serial bus) connector. USB flash drives are typically removable and rewritable, much smaller than a floppy disk and weigh less than 2 ounces.

Storage capacities typically range from 64 MB to 32 GB or more. Some allow 1 million write or erase cycles and have 10-year data retention, connected by USB 1.1 or USB 2.0 or both. Pen drives offer potential advantages over other portable storage devices. They are more compact, faster, hold much more data, are more reliable for lack of moving parts, and have a more durable design.

USB ports appear on almost every current mainstream PC and laptop. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and other Unix-like systems. A flash drive consists of a small printed circuit board typically in a plastic or metal casing and more recently in rubber casings to increase their robustness. This makes the drive sturdy enough to be carried about in a pocket. Most pen drives can be connected directly to a port on a personal computer.

An USB drive should never be removed without logging it off, especially when the drive has a write cache. The official way is through a symbol in the systray and some mouse clicks.