USB flash drive

A USB flash drive (UFD) (also thumb drive, memory stick, and pen drive/pendrive) is a data storage device that includes flash memory with an integrated USB interface. A typical USB drive is removable, rewritable, and smaller than an optical disc, and usually weighs less than 30 g (1 oz). Since first offered for sale in late 2000, the storage capacities of USB drives have ranged from 8 megabytes to 1 terabyte (TB). As of 2024, 4 TB flash drives were the largest currently in production. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to physically last between 10 and 100 years under normal circumstances (shelf storage time).

Common uses of USB flash drives are for storage, supplementary back-ups, and transferring of computer files. Compared with floppy disks or CDs, they are smaller, faster, have significantly more capacity, and are more durable due to a lack of moving parts. Additionally, they are less vulnerable to electromagnetic interference than floppy disks, and are unharmed by surface scratches (unlike CDs). However, as with any flash storage, data loss from bit leaking due to prolonged lack of electrical power and the possibility of spontaneous controller failure due to poor manufacturing could make it unsuitable for long-term archiving of data. The ability to retain data is affected by the controller's firmware, internal data redundancy, and error correction algorithms.

Until about 2005, most desktop and laptop computers were supplied with floppy disk drives in addition to USB ports, but floppy disk drives became obsolete after widespread adoption of USB ports and the larger USB drive capacity compared to the "1.44 megabyte" 3.5-inch floppy disk.

USB flash drives use the USB mass storage device class standard, supported natively by modern operating systems such as Windows, Linux, macOS and other Unix-like systems, as well as many BIOS boot ROMs. USB drives with USB 2.0 support can store more data and transfer faster than much larger optical disc drives like CD-RW or DVD-RW drives and can be read by many other systems such as the Xbox One, PlayStation 4, DVD players, automobile entertainment systems, and in a number of handheld devices such as smartphones and tablet computers, though the electronically similar SD card is better suited for those devices, due to their standardized form factor, which allows the card to be housed inside a device without protruding.

A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case, which can be carried in a pocket or on a key chain, for example. Some are equipped with an I/O indication LED that lights up or blinks upon access. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing connection with a port on a personal computer, but drives for other interfaces also exist (e.g. micro-USB and USB-C ports). USB flash drives draw power from the computer via the USB connection. Some devices combine the functionality of a portable media player with USB flash storage; they require a battery only when used to play music on the go.

The basis for USB flash drives is flash memory, a type of floating-gate semiconductor memory invented by Fujio Masuoka in the early 1980s. Flash memory uses floating-gate MOSFET transistors as memory cells. In the 1995, a group of companies including IBM, Microsoft, Intel and NEC were working on the development of Universal Serial Bus (USB).

Multiple individuals have staked a claim to having invented the USB flash drive. On April 5, 1999, Amir Ban, Dov Moran, and Oron Ogdan of M-Systems, an Israeli company, filed a patent application entitled "Architecture for a Universal Serial Bus-Based PC Flash Disk" that combined flash memory storage with USB connector through a USB controller. The patent was subsequently granted on November 14, 2000, and these individuals have often been recognized as the inventors of the USB flash drive. Also in 1999, Shimon Shmueli, an engineer at IBM, submitted an invention disclosure asserting that he had invented the USB flash drive.

Netac Technology filed a patent application for its USB storage device on 14 November 1999, and was granted by the Chinese government in July 2002. Netac went on to obtain another patent in the United States on 13 October 2000 and application was granted on 7 December 2004. Netac's patent was disputed by M-systems and Singaporean company Trek 2000 but Netac remained as the holder of the patent. Netac went on to file legal battles domestically in China and overseas and had received patent royalties and licensing fees in return. The company also invented a feature called "write-protect" function on its USB memory sticks. A Singaporean company named Trek 2000 International is the first company known to have sold a USB flash drive, which it trademarked as "ThumbDrive", and has also maintained that it is the original inventor of the device. Trek 2000 obtained a Singapore patent for the "ThumbDrive" in April 2002. It went on to sue the other four companies for infringing its patent. Singapore High Court ruled in Trek 2000's favour in 2005. After that, Trek 2000 went on to obtain patents from other countries. However, in 2005, Trek 2000 experienced a setback when its USB storage device patent was revoked in the United Kingdom. Pua Khein-Seng, a Malaysian engineer, who co-founded a Taiwanese company named Phison invented a USB Drive system on a chip (SoC) design in 2001 which uses a single chip instead of multiple chips used by its competitiors, which reduces the size and cost of production of flash drives.