Flash memory combines a number of older technologies, with lower cost, lower power consumption and small size made possible by advances in microprocessor technology. The memory storage was based on earlier EPROM and EEPROM technologies. These had limited capacity, were slow for both reading and writing, required complex high-voltage drive circuitry, and could be re-written only after erasing the entire contents of the chip.

When used in the same manner as external rotating drives (hard drives, optical drives, or floppy drives), i.e. in ignorance of their technology, USB drives' failure is more likely to be sudden: while rotating drives can fail instantaneously, they more frequently give some indication (noises, slowness) that they are about to fail, often with enough advance warning that data can be removed before total failure. USB drives give little or no advance warning of failure. Furthermore, when internal wear-leveling is applied to prolong life of the flash drive, once failure of even part of the memory occurs it can be difficult or impossible to use the remainder of the drive, which differs from magnetic media, where bad sectors can be marked permanently not to be used.[74]
^{Counterfeit USB flash drives are sometimes sold with claims of having higher capacities than they actually have. These are typically low capacity USB drives which are modified so that they emulate larger capacity drives (for example, a 2 GB drive being marketed as a 64 GB drive). When plugged into a computer, they report themselves as being the larger capacity they were sold as, but when data is written to them, either the write fails, the drive freezes up, or it overwrites existing data. Software tools exist to check and detect fake USB drives,[43][44] and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.[45]}
Our tester highly recommended this flash drive for iOS mobile users: “The iXpand is a great resource for backing up media files and for expanding storage, as well as transferring files to a PC.” He added, “The Drive App is easy to navigate and copy files with, as well as operate the camera and play music and video files.” On the other hand, our reviewer reported, “The 30 MB/s write speed on PC is far from horrible but definitely slow for the asking price, and we calculated only about a 12 MB/s when connected to an iOS device.” He ultimately concluded, “A slightly cheaper price would make it the surefire winner in the Lightning connector category.”
Quickly transfer files to and from your laptop or desktop using this SanDisk Ultra SDCZ48-064G-A46 USB 3.0 flash drive that features a read speed of up to 80MB/sec. The 64GB capacity offers ample storage space. (Ten times faster than USB 2.0 drives. Write speeds up to 10 times faster than Cruzer USB 2.0 drive.)* *USB 3.0 port required. Based on internal testing; performance may be lower depending upon host device.
A USB flash drive[note 1] is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than 30 g (1 oz). Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 GB were frequently sold, while 512 GB and 1 TB units were less frequent.[2][3] As of 2018, 2 TB flash drives were the largest available in terms of storage capacity.[4] Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances (shelf storage time[5]).
Flash memory cards, e.g., Secure Digital cards, are available in various formats and capacities, and are used by many consumer devices. However, while virtually all PCs have USB ports, allowing the use of USB flash drives, memory card readers are not commonly supplied as standard equipment (particularly with desktop computers). Although inexpensive card readers are available that read many common formats, this results in two pieces of portable equipment (card plus reader) rather than one.
Installers of some operating systems can be stored to a flash drive instead of a CD or DVD, including various Linux distributions, Windows 7 and newer versions, and macOS. In particular, Mac OS X 10.7 is distributed only online, through the Mac App Store, or on flash drives; for a MacBook Air with Boot Camp and no external optical drive, a flash drive can be used to run installation of Windows or Linux.
Flash drives can be defragmented. There is a widespread opinion that defragmenting brings little advantage (as there is no mechanical head that moves from fragment to fragment), and that defragmenting shortens the life of the drive by making many unnecessary writes.[37] However, some sources claim[38] that defragmenting a flash drive can improve performance (mostly due to improved caching of the clustered data), and the additional wear on flash drives may not be significant.
^{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. 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. 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.}
Some file systems are designed to distribute usage over an entire memory device without concentrating usage on any part (e.g., for a directory) to prolong the life of simple flash memory devices. Some USB flash drives have this 'wear leveling' feature built into the software controller to prolong device life, while others do not, so it is not necessarily helpful to install one of these file systems.[39]
Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second (MB/s), megabits per second (Mbit/s), or in optical drive multipliers such as "180X" (180 times 150 KiB/s).[19] File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30 MB/s and write at about half that rate, which was about 20 times faster than the theoretical transfer rate achievable by the previous model, USB 1.1, which is limited to 12 Mbit/s (1.5 MB/s) with accounted overhead.[20] The effective transfer rate of a device is significantly affected by the data access pattern.[21]

Macbooks require a USB Type-C device, which is where this swivel dual flash drive from Silicon Power comes in handy. It features a dual interface with USB Type-C and USB Type-A 3.0 ports on opposite ends of a compact device. The 360-degree swivel cap protects whichever connector is not in use and attaches easily to keychains. The C80 doesn’t require any special drivers or software to work; just plug it into the port and it is ready to go. But it has an optional file management app, which is a free and simple automatic file categorization that puts your work in the appropriate folders. Expect fast read and write speeds and 64 GB of storage to hold all your photos and files.