View source for Engineering:USB flash drive

{{Short description|Data storage device}}
 [[File:SanDisk-Cruzer-USB-4GB-ThumbDrive.jpg|thumb|A SanDisk Cruzer USB drive from 2011, with 4&nbsp;GB of storage capacity]]
[[File:SanDisk Ultra Flair flash drive.jpg|thumb|A SanDisk Ultra Flair USB drive from 2020, attached to a HP laptop]]

A '''USB flash drive''' (also called a '''thumb drive''')<ref>{{cite web |title=thumb drive |url=https://www.merriam-webster.com/dictionary/thumb%20drive |website=Merriam-Webster |access-date=December 11, 2021}}</ref>{{#tag:ref|'''Jumpdrive''' is a [[Company:Lexar|Lexar]] trademark.<ref>{{cite web |title=Jumpdrive |url=https://www.merriam-webster.com/dictionary/Jumpdrive |website=Merriam-Webster |access-date=December 11, 2021}}</ref> Less common names are '''disk key''', '''disk on key''' (after the original M-Systems DiskOnKey drive from 2000),<ref name=":0">{{Cite news|url=https://www.newyorker.com/tech/annals-of-technology/object-of-interest-the-flash-drive|title=Object of Interest: The Flash Drive|magazine=The New Yorker|access-date=2018-10-04|language=en-US}}</ref> '''flash stick''', '''gig stick''', '''memory stick''' (not to be confused with the Sony Memory Stick), '''pen drive''', '''USB drive''', '''USB key''', '''USB memory''', or '''USB stick'''<!-- for adding alternative names, please see existing consensus at Talk:USB flash drive/Archive 3 -->. For an incomplete list of alternative names, see the [//en.wikipedia.org/w/index.php?title=Special:WhatLinksHere/USB_flash_drive&hidetrans=1&hidelinks=1&limit=500 list of redirects] to this article.|group=note| group = "note"}} is a [[Engineering:Data storage device|data storage device]] that includes [[Flash memory|flash memory]] with an integrated [[Engineering:USB|USB]] interface. It is typically removable, rewritable and much smaller than an [[Engineering:Optical disc|optical disc]]. Most weigh less than {{cvt|1|oz|sigfig=1|order=flip}}. 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 [[Gigabyte|gigabyte]]s (GB<ref>1 GB = 1 billion bytes</ref>) were frequently sold, while 512&nbsp;GB and 1&nbsp;[[Terabyte|terabyte]] (TB<ref>1 TB = 1 thousand gigabytes</ref>) units were less frequent.<ref name="digitaltrends.com">{{cite web|last1=Madison|first1=Alex|title=Keychain Not Included: The Five Highest-Capacity USB Flash Drives for Your Digital Life|url=http://www.digitaltrends.com/computing/highest-capacity-usb-flash-drives/|website=Digital Trends|access-date=17 October 2016|date=2016-07-09}}</ref><ref name="techradar1">{{cite web|last1=Athow|first1=Desire|title=The best USB flash drives 2016|url=http://www.techradar.com/news/computing-components/storage/what-s-the-best-usb-stick-11-drives-tested-695094|website=Tech Radar|access-date=17 October 2016|date=2016-07-04}}</ref> As of 2018, 2&nbsp;TB flash drives were the largest available in terms of storage capacity.<ref>{{Cite news|url=https://www.digitaltrends.com/computing/largest-flash-drives/|title=The Largest Flash Drives {{!}} Digital Trends|date=2018-07-23|work=Digital Trends|access-date=2018-10-09|language=en-US}}</ref> 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 ([[Engineering:Digital permanence|shelf storage time]]<ref name="wcycles">USB flash drives allow reading, writing, and erasing of data, with some allowing 1 million write/erase cycles in each cell of memory: if there were 100 uses per day, 1 million cycles could span 10,000 days or over 27 years. Some devices level the usage by auto-shifting activity to underused sections of memory.</ref>).

Common uses of USB flash drives are for storage, supplementary back-ups, and transferring of [[Computer file|computer file]]s. Compared with [[Floppy disk|floppy disk]]s or [[Engineering:Compact disc|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 [[Engineering:Electromagnetic interference|electromagnetic interference]] than floppy disks, and are unharmed by surface scratches (unlike CDs). However, as with any flash storage, data loss from [[Data degradation#In storage|bit leaking]] due to prolonged lack of electrical power and the possibility of spontaneous [[Flash memory controller|controller]] [[Engineering:Failure of electronic components|failure]] due to poor manufacturing could make it unsuitable for long-term archival of data<!--Wikipedia:Manual of Style/Linking#Redirects § 2 as of revision 1059369165 -->. The ability to retain data is affected by the controller's [[Firmware|firmware]], internal [[Data redundancy|data redundancy]], and error correction algorithms.<ref>{{cite web |title=USB Flash drive Resurrection |url=https://sectechno.com/usb-flash-drive-resurrection/ |website=SecTechno |access-date=12 December 2021 |date=29 May 2011}}</ref><ref name=ni12>{{Cite web|date=2020-07-23|title=Understanding Life Expectancy of Flash Storage|url=https://www.ni.com/en-us/support/documentation/supplemental/12/understanding-life-expectancy-of-flash-storage.html|access-date=2020-12-19|website=www.ni.com|language=en}}</ref>

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" (1440 [[Kilobyte|kilobyte]]) 3.5-inch floppy disk.

USB flash drives use the [[Engineering:USB mass storage device class|USB mass storage device class]] standard, supported natively by modern [[Operating system|operating system]]s such as [[Software:Microsoft Windows|Windows]], [[Software:Linux|Linux]], {{nowrap|[[Software:MacOS|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 [[Engineering:Xbox One|Xbox One]], [[Engineering:PlayStation 4|PlayStation 4]], DVD players, automobile entertainment systems, and in a number of handheld devices such as smartphones and tablet computers, though the electronically similar [[Engineering:SD card|SD card]] is better suited for those devices, due to their standardized form factor, which allows it to be housed inside a device without protruding.

A flash drive consists of a small [[Engineering:Printed circuit board|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 [[Engineering:LED|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 [[Engineering:Portable media player|portable media player]] with USB flash storage; they require a battery only when used to play music on the go.<!-- There are more devices than just this, TomTom ONE for example.  I wonder if specific products (e.g., music player) should be included --><!-- From the article for Kingston -->

==History==
The basis for USB flash drives is [[Flash memory|flash memory]], a type of floating-gate [[Engineering:Semiconductor memory|semiconductor memory]] invented by Fujio Masuoka in the early 1980s. Flash memory uses [[Engineering:Floating-gate MOSFET|floating-gate MOSFET]] transistors as [[Memory cell (computing)|memory cells]].<ref>{{cite web |title=Flash Memory |url=http://www.iue.tuwien.ac.at/phd/windbacher/node14.html |website=TU Wien |access-date=4 December 2019}}</ref><ref>{{cite book |last1=Harris |first1=David |last2=Harris |first2=Sarah |title=Digital Design and Computer Architecture |date=2010 |publisher=Morgan Kaufmann |isbn=978-0-08-054706-0 |pages=263–4 |url=https://books.google.com/books?id=5X7JV5-n0FIC&pg=PA263 |language=en}}</ref>

Multiple individuals have staked a claim to being the inventor of the USB flash drive.  On April 5, 1999, Amir Ban, Dov Moran, and Oron Ogdan of [[Company:M-Systems|M-Systems]], an Israeli company, filed a patent application entitled "Architecture for a Universal Serial Bus-Based PC Flash Disk".<ref>{{Cite patent|title=Architecture for a universal serial bus-based PC flash disk|gdate=1999-04-05|url=https://patents.google.com/patent/US6148354A/en}}</ref><ref name=":0" /> The patent was subsequently granted on November 14, 2000 and these individuals have often been recognized as the inventors of the USB flash drive.<ref>{{Cite web|title=Who invented the Thumb-Drive?|url=https://kodakdigitizing.com/blogs/news/who-invented-the-thumb-drive|access-date=2021-03-25|website=Kodak Digitizing}}</ref> Also in 1999, Shimon Shmueli, an engineer at IBM, submitted an invention disclosure asserting that he had invented the USB flash drive.<ref name=":0" /><ref>{{Cite web|date=2015-04-23|title=History Of The Flash Drive|url=https://mediafast.com/history-of-the-flash-drive/|access-date=2021-03-25|website=MediaFast|language=en-US}}</ref> A Singaporean company named Trek 2000 International is the first company known to have sold a USB flash drive, and has also maintained that it is the original inventor of the device.<ref>{{Cite web|title=Who Invented the USB Flash Drive? - Premium USB|url=https://www.premiumusb.com/blog/who-invented-the-usb-flash-drive|access-date=2021-03-25|website=www.premiumusb.com}}</ref> Finally Pua Khein-Seng, a Malaysian engineer, has also been recognized by some as a possible inventor of the device.<ref>{{Cite web|title='Father of pen drive' now a Datuk {{!}} The Star|url=https://www.thestar.com.my/news/nation/2012/07/17/father-of-pen-drive-now-a-datuk|access-date=2021-03-25|website=www.thestar.com.my}}</ref>

Given these competing claims to inventorship, patent disputes involving the USB flash drive have arisen over the years.  Both Trek 2000 International and Netac Technology have accused others of infringing their patents on the USB flash drive.<ref>{{Cite web|title=Patent Expires for Flash Memory Sticks, Invented by a Chinese Company-Jiemian Global|url=https://en.jiemian.com/article/3723200.html|access-date=2021-03-25|website=en.jiemian.com}}</ref><ref>{{cite news| url=http://www.bangkokpost.com/breaking_news/breakingnews.php?id=70859| title=Singapore firm wins patent on thumb drive |newspaper=The Straits Times | access-date=2006-08-01}}</ref><ref>{{cite news| url=http://eresources.nlb.gov.sg/infopedia/articles/SIP_1071_2010-03-23.html| work=nlb.gov.sg | title= Trek 2000 and the ThumbDrive | date=March 23, 2010 |access-date=2016-06-25}}</ref> However, despite these lawsuits, the question of who was the first to invent the USB flash drive has not been definitively settled and multiple claims persist.

===Technology improvements===
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&nbsp;[[Kibibyte|KiB]]/s).<ref>{{cite web|url=http://vampiric.us/index.php/articles/hardware/optical/opticalthroughpm|title=4 Optical Drives through Port Multiplier|website=vampiric.us|archive-url=https://web.archive.org/web/20141228185855/http://vampiric.us/index.php/articles/hardware/optical/opticalthroughpm|archive-date=28 December 2014|url-status=dead|access-date=22 December 2014|df=dmy-all}}</ref> File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30&nbsp;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&nbsp;1.1, which is limited to 12&nbsp;Mbit/s (1.5&nbsp;MB/s) with accounted overhead.<ref>{{cite web|url=http://www.diffen.com/difference/USB_1.0_vs_USB_2.0|title=USB 1.0 vs. USB 2.0|publisher=Diffen|access-date=22 December 2014}}</ref> The effective transfer rate of a device is significantly affected by the data access pattern.<ref>{{cite web|url=https://www.usenix.org/legacy/event/usenix09/tech/full_papers/vandebogart/vandebogart_html/index.html|title=Reducing Seek Overhead with Application-Directed Prefetching|website=Usenix.org|publisher=Usenix|access-date=22 December 2014}}</ref>

By 2002, USB flash drives had USB 2.0 connectivity, which has 480&nbsp;[[Megabit|Mbit]]/s as the transfer rate upper bound; after accounting for the protocol overhead {{cn-span|date=June 2022|text=that translates to a 35&nbsp;[[Megabyte|MB]]/s effective throughput.|reason=Previously used source not only gives a different value (40MB/s), but is itself linking Wikipedia as its source.}} That same year, Intel sparked widespread use of second generation USB by including them within its laptops.<ref name=":2">{{Cite news|url=https://www.cnet.com/news/want-a-laptop-with-usb-3-0-the-few-the-proud/|title=Want a laptop with USB 3.0? The few, the proud|date=2010-09-19|work=CNET|access-date=2018-10-10|language=en}}</ref>

By 2010, the maximum available storage capacity for the devices had reached upwards of 128&nbsp;GB.<ref name=":1">{{cite news|url=http://www.time.com/time/specials/packages/article/0,28804,2023689_2023703_2023613,00.html|archive-url=https://web.archive.org/web/20101028085259/http://www.time.com/time/specials/packages/article/0,28804,2023689_2023703_2023613,00.html|url-status=dead|archive-date=October 28, 2010|title=All-Time 100 Gadgets|date=2010-10-25|magazine=Time}}</ref> USB 3.0 was slow to appear in laptops. Through 2010, the majority of laptop models still contained only USB 2.0.<ref name=":2" />

In January 2013, tech company Kingston, released a flash drive with 1&nbsp;TB of storage.<ref>{{Cite news|url=https://www.usatoday.com/story/technologylive/2013/01/09/kingston-terabyte-flash-drive-ces/1820159/|title=Kingston unveils 1 terabyte flash drive|work=USA Today|access-date=2018-10-10|language=en}}</ref> The first USB 3.1 type-C flash drives, with read/write speeds of around 530&nbsp;MB/s, were announced in March 2015.<ref>{{cite web|url=http://www.gizmofusion.com/2015/03/pk-the-worlds-first-usb-kit-with-3-1-technology/|title=PK: the World's First USB Kit with 3.1 technology|access-date=1 June 2016}}</ref> By July 2016, flash drives with 8 to 256&nbsp;GB capacity were sold more frequently than those with capacities between 512 GB and 1 TB.<ref name="digitaltrends.com" /><ref name="techradar1" /> In 2017, Kingston Technology announced the release of a 2-TB flash drive.<ref>{{Cite news|url=https://money.cnn.com/2017/01/05/technology/kingston-technology-biggest-flash-drive-two-terabytes/index.html|title=The world's biggest flash drive can store more than 160 HD movies|last=Mullen|first=Jethro|work=CNNMoney|access-date=2018-10-10}}</ref>  In 2018, SanDisk announced a 1TB USB-C flash drive, the smallest of its kind.<ref>{{Cite web|url=https://www.theverge.com/circuitbreaker/2018/1/9/16867044/sandisk-prototype-1tb-usb-c-flash-drive-worlds-smallest-ces-2018|title=SanDisk shows off the world's smallest 1TB USB-C flash drive at CES|website=TheVerge.com|date=9 January 2018}}</ref>

{| border="1" cellpadding="4"  cellspacing="0" style="float:right; background:#f9f9f9; border:1px #aaa solid; border-collapse:collapse; margin-left:1em;"
|-
| style="background:#e7e7e7; text-align:center;" colspan="2"|
[[File:Usbkey internals.jpg|350px]]<br />'''Internals of a typical USB flash drive'''
|-
!1
|USB Standard-A, "male" plug
|-
!2
|USB mass storage controller device
|-
!3
|Test point
|-
!4
|[[Flash memory|Flash memory chip]]
|-
!5
|[[Engineering:Crystal oscillator|Crystal oscillator]]
|-
!6
|[[Engineering:LED|LED]] (Optional)
|-
!7
|[[Write protection|Write-protect]] switch (Optional)
|-
!8
|Space for second flash memory chip
|}

On a USB flash drive, one end of the device is fitted with a single Standard-A USB plug; some flash drives additionally offer a micro USB or USB-C plug, facilitating data transfers between different devices.<ref>{{cite web|last=Broida |first=Rick |url=http://reviews.cnet.com/8301-19736_7-57615094-251/pkparis-unveils-worlds-smallest-android-flash-drive/ |title=PKparis unveils world's smallest Android flash drive &#124; Android Atlas - CNET Reviews |publisher=Reviews.cnet.com |date=2013-12-10 |access-date=2014-02-19}}</ref>

==Technology==
{{Main|Flash memory|Engineering:USB}}
[[File:MicroSDFDrive.JPG|thumb|A Kingston [[Card reader|card reader]] which accepts Micro SD [[Memory card|memory card]]s (Transcend card shown partially inserted), and acts as a USB flash drive]]

On a USB flash drive, one end of the device is fitted with a single USB plug; some flash drives additionally offer a micro USB plug, facilitating data transfers between different devices.

Inside the casing is a small printed circuit board, which has some power circuitry and a small number of [[Engineering:Surface-mount technology|surface-mounted]] [[Engineering:Integrated circuit|integrated circuit]]s (ICs).{{Citation needed|date=October 2018}} Typically, one of these ICs provides an interface between the USB connector and the onboard memory, while the other is the [[Flash memory|flash memory]]. Drives typically use the [[Engineering:USB mass storage device class|USB mass storage device class]] to communicate with the host.<ref>{{Cite web|url=https://www.premiumusb.com/blog/whats-inside-a-usb-drive|title=What's Inside a USB Drive? |website=PremiumUSB.com |access-date=2018-10-10}}</ref>

=== Flash memory ===
Flash memory combines a number of older technologies, with lower cost, lower power consumption and small size made possible by advances in [[Engineering:Semiconductor device fabrication|semiconductor device fabrication]] technology. The memory storage was based on earlier [[Engineering:EPROM|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.

Hardware designers later developed EEPROMs with the erasure region broken up into smaller "fields" that could be erased individually without affecting the others. Altering the contents of a particular memory location involved copying the entire field into an off-chip buffer memory, erasing the field, modifying the data as required in the buffer, and re-writing it into the same field. This required considerable computer support, and PC-based EEPROM flash memory systems often carried their own dedicated microprocessor system. Flash drives are more or less a miniaturized version of this.

The development of high-speed serial data interfaces such as USB made semiconductor memory systems with serially accessed storage viable, and the simultaneous development of small, high-speed, low-power microprocessor systems allowed this to be incorporated into extremely compact systems. Serial access requires far fewer electrical connections for the memory chips than does [[Random-access memory|parallel access]], which has simplified the manufacture of multi-[[Gigabyte|gigabyte]] drives.

Computers access {{as of|2009|alt=modern}} flash memory systems very much like hard disk drives, where the [[Flash memory controller|controller system]] has full control over where information is actually stored. The actual EEPROM writing and erasure processes are, however, still very similar to the earlier systems described above.

Many low-cost [[MP3 player]]s simply add extra software and a battery to a standard flash memory control microprocessor so it can also serve as a music playback decoder. Most of these players can also be used as a conventional flash drive, for storing files of any type.

===Essential components===
[[File:Kingston DataTraveler flash drive disassembled.jpg|thumb|The internal mechanical and electronic parts of a Kingston 2&nbsp;GB flash drive]]

There are typically five parts to a flash drive:

* USB plug{{snd}} provides a physical interface to the host computer. Some USB flash drives use USB plug that does not protect the contacts, with the possibility of plugging it into the USB port in the wrong orientation, if the connector type is not symmetrical.
* USB mass storage controller{{snd}} a small [[Engineering:Microcontroller|microcontroller]] with a small amount of on-chip [[Read-only memory|ROM]] and RAM.
* NAND flash memory chip(s){{snd}} stores data (NAND flash is typically also used in [[Engineering:Digital camera|digital camera]]s).
* [[Engineering:Crystal oscillator|Crystal oscillator]]{{snd}} produces the device's main [[Clock signal|clock signal]] and controls the device's data output through a [[Engineering:Phase-locked loop|phase-locked loop]].
* Cover{{snd}} typically made of plastic or metal, protecting the electronics against mechanical stress and even possible short circuits.

===Additional components===
The typical device may also include:

[[File:USB flash drive2.jpg|thumb|The front and rear side of a USB flash drive with the casing removed]]

* [[Engineering:Jumper (computing)|Jumpers]] and test pins – for testing during the flash drive's manufacturing or loading code into its [[Engineering:Microcontroller|microcontroller]].
* [[Engineering:Light-emitting diode|LEDs]] – indicate data transfers or data reads and writes.
* [[Write protection|Write-protect]] switches – Enable or disable writing of data into memory.
* Unpopulated space – provides space to include a second memory chip. Having this second space allows the manufacturer to use a single printed circuit board for more than one storage size device.
* USB connector cover or cap – reduces the risk of damage, prevents the entry of dirt or other contaminants, and improves overall device appearance. Some flash drives use retractable USB connectors instead. Others have a swivel arrangement so that the connector can be protected without removing anything.
* Transport aid – the cap or the body often contains a hole suitable for connection to a key chain or lanyard. Connecting the cap, rather than the body, can allow the drive itself to be lost.
* Some drives offer expandable storage via an internal [[Memory card|memory card]] slot, much like a memory [[Card reader|card reader]].<ref>[http://www.ces-show.com/2006/review/pny/pny_usb_flash_drive.html PNY USB Flash Drive – CES 2006 – LetsGoDigital]. Ces-show.com. Retrieved on 2011-05-18.</ref><ref>[http://www.techchee.com/2008/05/20/bluetrek-bizz-an-expandable-usb-drive-and-a-bluetooth-headset-in-one/ BlueTrek Bizz – an expandable USB  and a Bluetooth headset in one] {{Webarchive|url=https://web.archive.org/web/20140829094528/http://www.techchee.com/2008/05/20/bluetrek-bizz-an-expandable-usb-drive-and-a-bluetooth-headset-in-one/ |date=2014-08-29 }}. TechChee.com (2008-05-20). Retrieved on 2011-05-18.</ref>

===Size and style of packaging===
[[File:sushiusb.jpg|thumb|Flash drives come in various shapes and sizes, sometimes bulky or novelty, such as the shape of ikura gunkan-maki.]]
[[File:Pendrive Shape of key.JPG|thumb|A USB flash drive in the shape of a key]]
[[File:Custom_USB_Drives.JPG|thumb|Assortment of USB flash drives]]

Most USB flash drives weigh less than {{cvt|1|oz|sigfig=1|order=flip}}.<ref>[http://peripherals.about.com/od/removablestorage/f/USBFAQ.htm Frequently Asked Questions About USB Flash Drives]. Retrieved on 2011-05-18.</ref> While some manufacturers are competing for the smallest size,<ref>{{cite magazine|last=Newman |first=Jared |url=http://www.pcworld.com/article/2937161/worlds-smallest-128gb-usb-30-drive-pkparis-k1-picks-a-fight-with-sandisk-ultra-fit.html |title=World's smallest 128GB USB 3.0 drive: PKParis K'1 picks a fight with SanDisk Ultra Fit |magazine=PCWorld |date=2015-06-17 |access-date=2017-06-06}}</ref> with the biggest memory, offering drives only a few millimeters larger than the USB plug itself,<ref>{{cite web|last=Marino |first=Robert |url=http://www.computershopper.com/slideshow/guide-the-20-best-small-usb-flash-drives/sandisk-ultra-fit-usb-3.0-flash-drive |title=Guide: The 20 Best Small USB Flash Drives |website=Computershopper.com |date=2015-09-10 |access-date=2017-06-06}}</ref> some manufacturers differentiate their products by using elaborate housings, which are often bulky and make the drive difficult to connect to the USB port. Because the [[Engineering:USB#USB connectors|USB port connectors]] on a computer housing are often closely spaced, plugging a flash drive into a USB port may block an adjacent port. Such devices may carry the USB logo only if sold with a separate extension cable. Such cables are USB-compatible but do not conform to the USB standard.<ref name=usb1>{{cite web |url=http://www.usb.org/developers/whitepapers/cablew~1.pdf |title=Archived copy |access-date=2016-06-01 |url-status=dead |archive-url=https://web.archive.org/web/20160304121924/http://www.usb.org/developers/whitepapers/cablew~1.pdf |archive-date=2016-03-04 }}</ref><ref name=usb2>{{cite web|url=http://www.usb.org/developers/docs/ecn1.pdf|title=USB 2.0 Specification Engineering Change Notice (ECN) #1: Mini-B connector|access-date=1 June 2016|archive-url=https://web.archive.org/web/20150412121600/http://www.usb.org/developers/docs/ecn1.pdf|archive-date=2015-04-12|url-status=dead}}</ref>

USB flash drives have been integrated into other commonly carried items, such as watches, pens, laser pointers, and even the Swiss Army Knife; others have been fitted with novelty cases such as toy cars or Lego bricks. USB flash drives with images of dragons, cats or aliens are very popular in Asia.<ref>[http://t3n.de/news/abgefahrene-usb-sticks-fernost-372900/ Bizarre USB flash drives from the Far East] {{Webarchive|url=https://web.archive.org/web/20120320213040/http://t3n.de/news/abgefahrene-usb-sticks-fernost-372900/ |date=2012-03-20 }} (German), t3n (2012-03-07). Retrieved on 2012-03-17.</ref> The small size, robustness and cheapness of USB flash drives make them an increasingly popular peripheral for [[Engineering:Case modding|case modding]].

===File system===
{{Main|Flash file system}}

Most flash drives ship preformatted with the [[FAT32]], or [[ExFAT|exFAT]] [[File system|file system]]s. The [[Philosophy:Omnipresence|ubiquity]] of the FAT32 file system allows the drive to be accessed on virtually any host device with USB support. Also, standard FAT maintenance utilities (e.g., ScanDisk) can be used to repair or retrieve [[Data corruption|corrupted data]]. However, because a flash drive appears as a USB-connected hard drive to the host system, the drive can be [[Disk formatting|reformatted]] to any file system supported by the host operating system.

====Defragmenting====
Flash drives can be [[Defragmentation|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.<ref>[http://ask-leo.com/should_i_defragment_my_usb_flash_drive.html Should I defragment my USB Flash drive?]. Ask-leo.com (2008-02-19). Retrieved on 2011-05-18.</ref>  However, some sources claim<ref>{{cite web |url=http://www.wizcode.com/articles/comments/flash_memory_fragmentation_myths_and_facts/ |title=Flash Memory Fragmentation – Myths and Facts |website=Wizcode.com |access-date=2017-06-06 |archive-url=https://web.archive.org/web/20170614154251/http://www.wizcode.com/articles/comments/flash_memory_fragmentation_myths_and_facts/ |archive-date=2017-06-14 }}</ref> 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.

====Even distribution====
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|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.<ref>{{cite web|url=http://download.micron.com/pdf/technotes/nand/tn2942_nand_wear_leveling.pdf|title=TN-29-42: Wear-Leveling Techniques in NAND Flash Devices<!-- Bot generated title -->|access-date=1 June 2016|url-status=dead|archive-url=https://web.archive.org/web/20120322130027/http://download.micron.com/pdf/technotes/nand/tn2942_nand_wear_leveling.pdf|archive-date=22 March 2012}}</ref>

<!-- Note: Please don't add JFFS or YAFFS references to this article. While these two file systems, designed to minimize the inherent weaknesses of flash memory (e.g., memory wear), can be used on a flash drive, they provide no significant benefit. These filesystems are intended to assist with directly addressed flash memory (e.g. SmartMedia through a raw reader). A flash drive's memory layout is abstracted from the host system in the USB mass storage class, and the flash drive's controller chip performs tasks similar to those JFFS and YAFFS are intended for.  -->

====Hard disk drive====
Sectors are 512 bytes long, for compatibility with hard disk drives, and the first sector can contain a [[Master boot record|master boot record]] and a [[Partition table|partition table]]. Therefore, USB flash units can be partitioned just like hard disk drives.

===Longevity===
The memory in flash drives was commonly engineered with [[Multi-level cell|multi-level cell]] (MLC) based memory that is good for around 3,000-5,000 program-erase cycles.<ref>{{cite web |url=http://www.anandtech.com/show/5734/kingston-hyperx-3k-240gb-ssd-review |title=Kingston HyperX 3K (240GB) SSD Review |publisher=Anandtec.com |date=2012-04-10 |access-date=2012-10-05}}</ref> Nowadays Triple-level Cell (TLC) is also often used, which has up to 500 write cycles per physical sector, while some high-end flash drives have single-level cell (SLC) based memory that is good for around 30,000 writes.<ref>{{Cite web|url=https://www.kingston.com/en/flashguide|title = Kingston's Flash Memory Guide - Kingston Technology}}</ref> There is virtually no limit to the number of reads from such flash memory, so a well-worn USB drive may be write-protected to help ensure the life of individual cells. <!-- This may be wrong: some say SSDs, which use the same flash memory, lose their data after 12 months if left unpowered.  <-- I've never seen or heard of that. -->

Estimation of flash memory endurance is a challenging subject that depends on the SLC/[[Multi-level cell|MLC]]/TLC memory type, size of the flash memory chips, and actual usage pattern. As a result, a USB flash drive can last from a few days to several hundred years.<ref>{{cite web|url=http://blog.bowtiepromotions.com/2013/04/how-long-does-a-usb-flash-drive-last-part-ii/|title=How Long Does a USB Flash Drive Last? (Part II)|work=Promotional USB Flash Drives and Accessories}}</ref>

Regardless of the endurance of the memory itself, the USB connector hardware is specified to withstand only around 1,500 insert-removal cycles.<ref>Blanchard, Richard (March 8th, 2007) [http://www.getusb.info/what-is-the-life-cycle-of-a-usb-flash-drive/ "What is the Life Cycle of a USB Flash Drive?"], GetUSB.info, retrieved June 14, 2010</ref>

==Counterfeit products==
Counterfeit USB flash drives are sometimes sold with claims of having higher capacities than they actually have. These are typically low capacity USB drives whose flash memory controller [[Firmware|firmware]] is modified so that they emulate larger capacity drives (for example, a 2&nbsp;GB drive being marketed as a 64&nbsp;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,<ref>[http://www.heise.de/software/download/h2testw/50539 "H2testw USB flash drive test tool"], www.heise.de, retrieved November 16, 2010</ref><ref>{{cite web |url=http://www.usbdev.ru/articles/detect_controller/ |language=ru |title=Определение модели контроллера и памяти флешки |date=20 February 2013 |trans-title=Detecting controller model and memory type of flash drive |publisher=usbdev.ru |access-date=2018-01-06}}</ref> and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.<ref>[http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ "About VID PID Repairing Counterfeit Flash Drives – Steps To Succeed"], fixfakeflash.wordpress.com, retrieved November 16, 2010</ref>

==File transfer speeds==
Transfer speeds are technically determined by the slowest of three factors: the USB version used, the speed in which the USB controller device can read and write data onto the flash memory, and the speed of the [[Engineering:Bus (computing)|hardware bus]], especially in the case of add-on USB ports.

USB flash drives usually specify their read and write speeds in megabytes per second (MB/s); read speed is usually faster. These speeds are for optimal conditions; real-world speeds are usually slower. In particular, circumstances that often lead to speeds much lower than advertised are transfer (particularly writing) of many small files rather than a few very large ones, and mixed reading and writing to the same device.

In a typical well-conducted review of a number of high-performance USB&nbsp;3.0 drives, a drive that could read large files at 68&nbsp;MB/s and write at 46&nbsp;MB/s, could only manage 14&nbsp;MB/s and 0.3&nbsp;MB/s with many small files. When combining streaming reads and writes the speed of another drive, that could read at 92&nbsp;MB/s and write at 70&nbsp;MB/s, was 8&nbsp;MB/s. These differences differ radically from one drive to another; some drives could write small files at over 10% of the speed for large ones. The examples given are chosen to illustrate extremes.<ref>[http://www.tomshardware.com/reviews/usb-3.0-thumb-drive-flash-drive%2C2900.html Tom's Hardware: Nine USB 3.0 Flash Drives For Road Warriors], 26 April 2011</ref>

==Uses==

===Personal data transport===
The most common use of flash drives is to transport  and store personal files, such as documents, pictures and videos. Individuals also store medical information on flash drives for emergencies and disaster preparation.

===Secure storage of data, application and software files===
With wide deployment(s) of flash drives being used in various environments (secured or otherwise), the issue of data and information security remains important. The use of [[Biometrics|biometrics]] and [[Encryption|encryption]] is becoming the norm with the need for increased security for data; on-the-fly encryption systems are particularly useful in this regard, as they can transparently encrypt large amounts of data. In some cases a [[Engineering:USB flash drive security|secure USB drive]] may use a hardware-based encryption mechanism that uses a hardware module instead of software for strongly encrypting data. [[IEEE 1667]] is an attempt to create a generic authentication platform for USB drives. It is supported in [[Software:Windows 7|Windows 7]] and Windows Vista (Service Pack 2 with a hotfix).<ref>[http://support.microsoft.com/kb/981319 "An update is available that enables the support of Enhanced Storage devices in Windows Vista and in Windows Server 2008"]. Microsoft Support. November 23, 2010.</ref>

===Computer forensics and law enforcement===
A recent development for the use of a USB Flash Drive as an application carrier is to carry the [[Social:Computer Online Forensic Evidence Extractor|Computer Online Forensic Evidence Extractor]] (COFEE) application developed by [[Company:Microsoft|Microsoft]]. COFEE is a set of applications designed to search for and extract [[Computer forensics|digital evidence]] on computers confiscated from suspects.<ref>{{cite news|url=http://seattletimes.nwsource.com/html/microsoft/2004379751_msftlaw29.html |title=Microsoft device helps police pluck evidence from cyberscene of crime|newspaper=The Seattle Times|access-date=2008-04-29 | first=Benjamin J. | last=Romano | date=2008-04-29}}</ref> Forensic software is required not to alter, in any way, the information stored on the computer being examined. Other forensic suites run from [[CD-ROM]] or DVD-ROM, but cannot store data on the media they are run from (although they can write to other attached devices, such as external drives or [[Flash memory|memory sticks]]).

===Updating motherboard firmware===
[[Engineering:Motherboard|Motherboard]] firmware (including [[BIOS]] and UEFI) can be updated using USB flash drives.  Usually, new firmware image is downloaded and placed onto a [[FAT16]]- or [[FAT32]]-formatted USB flash drive connected to a system which is to be updated, and path to the new firmware image is selected within the update component of system's firmware.<ref>{{cite web
 |url         = http://www.northernmicro.com/en/support/tech-library/M4A785T-AS/WebHelp/asus_ez_flash_2_utility.htm
 |title       = ASUS EZ Flash 2 utility
 |date        = 2013-12-21
 |access-date  = 2014-01-16
 |publisher   = northernmicro.com
 |url-status=dead
 |archive-url  = https://web.archive.org/web/20120917005940/http://www.northernmicro.com/en/support/tech-library/M4A785T-AS/WebHelp/asus_ez_flash_2_utility.htm
 |archive-date = 2012-09-17
}}</ref>  Some motherboard manufacturers are also allowing such updates to be performed without the need for entering system's firmware update component, making it possible to easily recover systems with corrupted firmware.<ref>{{cite web
 | url = http://event.asus.com/2012/mb/usb_bios_flashback_guide/
 | title = How to Use USB BIOS Flashback
 | year = 2012 | access-date = 2014-01-16
 | publisher = ASUS
}}</ref>

Also, [[Company:Hewlett-Packard|HP]] has introduced a ''USB floppy drive key'', which is an ordinary USB flash drive with additional possibility for performing floppy drive emulation, allowing its usage for updating system firmware where direct usage of USB flash drives is not supported.  Desired mode of operation (either regular USB mass storage device or of floppy drive emulation) is made selectable by a sliding switch on the device's housing.<ref>{{Cite web |url=https://h20565.www2.hp.com/portal/site/hpsc/public/psi/home/?sp4ts.oid=3374182&ac.admitted=1389715656950.876444892.492883150 |title = HP USB Floppy Drive Key Support - HP Support Center |archive-url=https://archive.today/20140114162241/https://h20565.www2.hp.com/portal/site/hpsc/public/psi/home/?sp4ts.oid=3374182&ac.admitted=1389715656950.876444892.492883150 |archive-date=14 January 2014 |url-status=dead}}</ref><ref>{{cite web|url=http://www.slashgear.com/hp-usb-floppy-drive-key-2420273/ |title=HP USB Floppy Drive Key |date=24 October 2008 |publisher=SlashGear |access-date=2017-06-06}}</ref>

===Booting operating systems===
<!-- This image is of a drive not supported by Microsoft any longer, so it should be replaced by something supported
[[File:Windows To Go USB Drive.png|thumb|Bootable Windows To Go USB flash drive|link=Windows To Go]] -->
Most current PC firmware permits [[Booting|booting]] from a USB drive, allowing the launch of an operating system from a bootable flash drive. Such a configuration is known as a [[Software:Live USB|Live USB]].<ref>[http://www.pcworld.com/article/2152040/aomei-partition-assistant-review-windows-to-go-no-longer-just-for-enterprise-users.html  Boot Windows from a certified USB flash drive]. Retrieved on 14 May 2014</ref>

Original flash memory designs had very limited estimated lifetimes. The failure mechanism for flash memory cells is analogous to a [[Fatigue (material)|metal fatigue]] mode; the device fails by refusing to write new data to specific cells that have been subject to many read-write cycles over the device's lifetime. Premature failure of a "live USB" could be circumvented by using a flash drive with a write-lock switch as a WORM device, identical to a live CD. Originally, this potential failure mode limited the use of "live USB" system to special-purpose applications or temporary tasks, such as:

* Loading a minimal, hardened [[Software:Kernel (operating system)|kernel]] for embedded applications (e.g., network router, firewall).
* Bootstrapping an operating system install or [[Disk cloning|disk cloning]] operation, often across a network.
* Maintenance tasks, such as virus scanning or low-level data repair, without the primary host operating system loaded.

{{As of|2011}}, newer flash memory designs have much higher estimated lifetimes. Several manufacturers are now offering warranties of 5 years or more. Such warranties should make the device more attractive for more applications. By reducing the probability of the device's premature failure, flash memory devices can now be considered for use where a magnetic disk would normally have been required. Flash drives have also experienced an exponential growth in their storage capacity over time (following the Moore's Law growth curve). As of 2013, single-packaged devices with capacities of 1&nbsp;[[Terabyte|TB]] are readily available,<ref name="tomshardware-1tb">{{cite web|author=Jane McEntegart |url=http://www.tomshardware.com/news/1TB-USB-Large-Capacity-Thumb-Drive-512GB-USB-DataTraveler-HyperX-Predator-USB-3,20278.html |title=Hands-on with Kingston's 1TB USB Stick |publisher=Tomshardware.com |date=2013-01-08 |access-date=2014-03-08}}</ref> and devices with 16&nbsp;GB capacity are very economical. Storage capacities in this range have traditionally been considered to offer adequate space, because they allow enough space for both the operating system software and some free space for the user's data.

===Operating system installation media===
Installers of some operating systems can be stored to a flash drive instead of a CD or DVD, including various [[Software:Linux distribution|Linux distribution]]s, Windows&nbsp;7 and newer versions, and [[Software:MacOS|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 [[Software:Boot Camp|Boot Camp]] and no external optical drive, a flash drive can be used to run installation of Windows or Linux.

However, for installation of Windows 7 and later versions, using USB flash drive with hard disk drive emulation as detected in PC's firmware is recommended in order to boot from it. Transcend is the only manufacturer of USB flash drives containing such feature.

Furthermore, for installation of [[Software:Windows XP|Windows XP]], using USB flash drive with storage limit of at most 2 GB is recommended in order to boot from it.

===Windows ReadyBoost===
In [[Software:Windows Vista|Windows Vista]] and later versions, [[Software:ReadyBoost|ReadyBoost]] feature allows flash drives (from 4&nbsp;GB in case of Windows Vista) to augment operating system memory.<ref name="test">{{cite web |first=Martin |last=Brinkmann |title=Windows 7 to Extend Readyboost |url=http://windows7news.com/2008/11/01/windows-7-to-extend-readyboost/ |publisher=Windows 7 News |date=2008-11-01 |access-date=2009-05-12 |url-status=dead |archive-url=https://web.archive.org/web/20090106073155/http://windows7news.com/2008/11/01/windows-7-to-extend-readyboost/ |archive-date=2009-01-06 }}</ref>

===Application carriers===
Flash drives are used to carry [[Software:List of portable software|applications]] that run on the host computer without requiring installation. While any standalone application can in principle be used this way, many programs store data, configuration information, etc. on the hard drive and [[Software:Windows Registry|registry]] of the host computer.

The [[Software:U3|U3]] company works with drive makers (parent company [[Company:SanDisk|SanDisk]] as well as others) to deliver custom versions of applications designed for [[Software:Microsoft Windows|Microsoft Windows]] from a special flash drive; U3-compatible devices are designed to autoload a menu when plugged into a computer running Windows. Applications must be modified for the U3 platform not to leave any data on the host machine. U3 also provides a software framework for [[Independent software vendor|independent software vendor]]s interested in their platform.

[[Software:Ceedo|Ceedo]] is an alternative product, with the key difference that it does not require Windows applications to be modified in order for them to be carried and run on the drive.

Similarly, other [[Software:Application virtualization|application virtualization]] solutions and [[Software:Portable application creators|portable application creators]], such as [[Software:VMware ThinApp|VMware ThinApp]] (for Windows) or RUNZ (for Linux) can be used to run software from a flash drive without installation.

In October 2010, [[Company:Apple Inc.|Apple Inc.]] released their newest iteration of the MacBook Air, which had the system's restore files contained on a USB hard drive rather than the traditional install CDs, due to the Air not coming with an optical drive.<ref>[https://techcrunch.com/2010/10/20/a-compact-death/ "Yep, Apple Killed The CD Today"]. TechCrunch.com. October 20, 2010.</ref>

A wide range of [[Software:Portable application|portable application]]s which are all free of charge, and able to run off a computer running Windows without storing anything on the host computer's drives or registry, can be found in the [[Software:List of portable software|list of portable software]].

===Backup===
Some [[Finance:Value-added reseller|value-added reseller]]s are now using a flash drive as part of small-business [[Turnkey|turnkey]] solutions (e.g., [[Point of sale|point-of-sale]] systems). The drive is used as a [[Backup|backup]] medium: at the close of business each night, the drive is inserted, and a [[Database|database]] backup is saved to the drive. Alternatively, the drive can be left inserted through the business day, and data regularly updated. In either case, the drive is removed at night and taken offsite.

* This is simple for the end-user, and more likely to be done.
* The drive is small and convenient, and more likely to be carried off-site for safety.
* The drives are less fragile mechanically and magnetically than tapes.
* The capacity is often large enough for several backup images of critical data.
* Flash drives are cheaper than many other backup systems.

Flash drives also have disadvantages. They are easy to lose and facilitate unauthorized backups.  A lesser setback for flash drives is that they have only one tenth the capacity of hard drives manufactured around their time of distribution.

=== Password Reset Disk ===
Password Reset Disk is a feature of the Windows operating system. If a user sets up a Password Reset Disk, it can be used to reset the password on the computer it was set up on.

===Audio players===
[[File:Sony Walkman NWZ-B183.jpg|thumb|A contemporary thumb drive styled solid-state digital audio player (Sony Walkman B180 Series)]]
Many companies make small solid-state digital audio players, essentially producing flash drives with sound output and a simple user interface. Examples include the [[Engineering:Creative MuVo|Creative MuVo]], [[Engineering:Philips GoGear|Philips GoGear]] and the first generation iPod shuffle. Some of these players are true USB flash drives as well as music players; others do not support general-purpose data storage. Other applications requiring storage, such as [[Digital recording|digital voice or sound recording]], can also be combined with flash drive functionality.<ref>[http://www.olympusamerica.com/files/oima_cckb/VN-801PC_Instructions_EN.pdf From the manual for a typical digital voice recorder]: "Apart from using this unit as a recorder, you can use it as an external memory for your computer, as an external storage device."</ref>

Many of the smallest players are powered by a permanently fitted rechargeable battery, charged from the USB interface.  Fancier devices that function as a digital audio player have a USB host port (type A female typically).

===Media storage and marketing===
[[File:Wizo USB Stick.jpg|thumb|The German band Wizo's ''Stick EP'', released in 2004, was the first album released on a USB stick.]]
[[Digital audio]] files can be transported from one computer to another like any other file, and played on a compatible media player (with caveats for [[Engineering:Digital rights management|DRM]]-locked files). In addition, many home Hi-Fi and car stereo head units are now equipped with a USB port. This allows a USB flash drive containing media files in a variety of formats to be played directly on devices which support the format. Some LCD monitors for consumer HDTV viewing have a dedicated USB port through which music and video files can also be played without use of a personal computer.

Artists have sold or given away USB flash drives, with the first instance believed to be in 2004 when the German punk band Wizo released the ''Stick EP'', only as a USB drive. In addition to five high-bitrate [[MP3]]s, it also included a video, pictures, lyrics, and guitar tablature.<ref>{{cite news |url=http://www.spiegel.de/netzwelt/web/vorbespielter-usb-stick-musik-zum-loeschen-a-321682.html |title= Vorbespielter USB-Stick: Musik zum Löschen |last1=Patalong |first1=Frank |date=2004-10-06 |website=Spiegel Online |publisher=Der Spiegel |access-date=2014-06-26|language=de}}</ref> Subsequently, artists including Nine Inch Nails and Kylie Minogue<ref>[https://www.amazon.co.uk/X-USB-Kylie-Minogue/dp/B000YVCQZW X (USB): Kylie Minogue: Amazon.co.uk: Music]. Amazon.co.uk. Retrieved on 2011-05-18.</ref> have released music and promotional material on USB flash drives. The first USB album to be released in the UK was ''Kiss Does... Rave'', a compilation album released by the Kiss Network in April 2007.<ref>{{cite magazine|url=http://www.musicweek.com/news/read/albums-arrive-on-usb-format/035620|title=Albums arrive on USB format|date=23 April 2007|magazine=Music Week|issn=0265-1548|oclc=60620772|access-date=8 September 2013|archive-url=https://web.archive.org/web/20130908105902/http://www.musicweek.com/news/read/albums-arrive-on-usb-format/035620|archive-date=8 September 2013|url-status=live}}</ref>

===Brand and product promotion===
[[File:Ubuntu USB lanyard.jpg|thumb|100px|[[Software:Ubuntu (operating system)|Ubuntu]]-branded USB flash drive and lanyard.]]

The availability of inexpensive flash drives has enabled them to be used for       promotional and [[Finance:Marketing|marketing]] purposes, particularly within technical and computer-industry circles (e.g., technology trade shows). They may be given away for free, sold at less than wholesale price, or included as a bonus with another purchased product.

Usually, such drives will be custom-stamped with a company's logo, as a form of [[Finance:Advertising|advertising]]. The drive may be blank, or preloaded with graphics, documentation, web links, [[Software:Adobe Flash|Flash]] [[Engineering:Animation|animation]] or other [[Engineering:Multimedia|multimedia]], and free or demonstration software. Some preloaded drives are read-only, while others are configured with both read-only and user-writable segments. Such dual-partition drives are more expensive.<ref name=cp3>{{cite web |url=http://www.usbpromos.com/data-preloading-custom-usb-promos-usb-drives/ |title=Preloaded Flash Drives &#124; USB Promos |access-date=2016-02-09 |url-status=dead |archive-url=https://web.archive.org/web/20150423060855/http://www.usbpromos.com/data-preloading-custom-usb-promos-usb-drives |archive-date=2015-04-23 }}</ref>

Flash drives can be set up to automatically launch stored presentations, websites, articles, and any other software immediately on insertion of the drive using the Microsoft Windows [[Software:AutoRun|AutoRun]] feature.<ref name=cp1>[http://www.flashbay.com/usb_flash_drive_autorun_setup.html USB flash drive auto run setup], article from Flashbay.com</ref> Autorunning software this way does not work on all computers, and it is normally disabled by security-conscious users.

===Arcades===
In the [[Software:Arcade game|arcade game]] ''In the Groove'' and more commonly ''In The Groove 2'', flash drives are used to transfer high scores, screenshots, dance edits, and combos throughout sessions. As of software revision 21 (R21), players can also store custom songs and play them on any machine on which this feature is enabled. While use of flash drives is common, the drive must be [[Software:Linux|Linux]] compatible.{{Citation needed|date=March 2022}}

In the arcade games ''Pump it Up NX2'' and ''Pump it Up NXA'', a specially produced flash drive is used as a "save file" for unlocked songs, as well as for progressing in the WorldMax and Brain Shower sections of the game.{{Citation needed|date=March 2022}}

In the arcade game ''[[Software:Dance Dance Revolution X|Dance Dance Revolution X]]'', an exclusive USB flash drive was made by Konami for the purpose of the link feature from its Sony PlayStation 2 counterpart. However, any USB flash drive can be used in this arcade game.{{Citation needed|date=March 2022}}

==Conveniences==
Flash drives use little power, have no fragile moving parts, and for most capacities are small and light. Data stored on flash drives is impervious to mechanical shock, magnetic fields, [[Physics:Abrasion (mechanical)|scratches]] and dust. These properties make them suitable for transporting data from place to place and keeping the data readily at hand.

Flash drives also store data densely compared to many removable media. In mid-2009, 256&nbsp;GB drives became available, with the ability to hold many times more data than a [[Engineering:DVD|DVD]] (54 DVDs) or even a [[Engineering:Blu-ray|Blu-ray]] (10 BDs).<ref name="Kingston256GB">Baker, Jeff (July 20, 2009) [http://www.mobilewhack.com/kingston-unveils-256gb-thumb/ "Kingston unveils 256GB thumb"] {{Webarchive|url=https://web.archive.org/web/20120322203554/http://www.mobilewhack.com/kingston-unveils-256gb-thumb/ |date=2012-03-22 }}, MobileWhack.com</ref>

Flash drives implement the [[Engineering:USB mass storage device class|USB mass storage device class]] so that most modern [[Operating system|operating system]]s can read and write to them without installing [[Device driver|device driver]]s. The flash drives present a simple block-structured logical unit to the host operating system, hiding the individual complex implementation details of the various underlying flash memory devices. The operating system can use any [[File system|file system]] or block addressing scheme. Some computers can boot up from flash drives.

Specially manufactured flash drives are available that have a tough rubber or metal casing designed to be waterproof and virtually "unbreakable". These flash drives retain their memory after being submerged in water, and even through a machine wash. Leaving such a flash drive out to dry completely before allowing current to run through it has been known to result in a working drive with no future problems. Channel Five's ''Gadget Show'' cooked one of these flash drives with propane, froze it with [[Chemistry:Dry ice|dry ice]], submerged it in various acidic liquids, ran over it with a jeep and fired it against a wall with a mortar. A company specializing in recovering lost data from computer drives managed to recover all the data on the drive.<ref>{{YouTube|NyOFIH-6WGs|testing removable media}} on the Gadget Show.</ref> All data on the other removable storage devices tested, using optical or magnetic technologies, were destroyed.

==Comparison with other portable storage==
[[File:IBM card storage.NARA.jpg|thumb|[[Engineering:Punched card|Punched card]]s in storage at a U.S. Federal records center in 1959. All the data visible here could fit on a single flash drive.]]

===Tape===
The applications of current data tape cartridges hardly overlap those of flash drives: on tape, cost per gigabyte is very low for large volumes, but the individual drives and media are expensive. Media have a very high capacity and very fast transfer speeds, but store data [[Sequential access|sequentially]] and are very slow for random access of data. While disk-based backup is now the primary medium of choice for most companies, tape backup is still popular for taking data off-site for worst-case scenarios and for very large volumes (more than a few hundreds of TB). See [[Linear Tape-Open|LTO]] tapes.

===Floppy disk===
[[File:Flash Drive v. Floppy.jpg|thumb|Size comparison of a flash drive and a 3.5-inch floppy disk. The flash drive can hold about 11,380 times more data.]]
[[Floppy disk]] drives are rarely fitted to modern computers and are obsolete for normal purposes, although internal and external drives can be fitted if required. Floppy disks may be the method of choice for transferring data to and from very old computers without USB or [[Booting|booting]] from floppy disks, and so they are sometimes used to change the firmware on, for example, [[BIOS]] chips. Devices with removable storage like older [[Company:Yamaha Corporation|Yamaha]] music keyboards are also dependent on floppy disks, which require computers to process them. Newer devices are built with USB flash drive support.

[[Floppy disk hardware emulator]]s exist which effectively utilize the internal connections and physical attributes of a floppy disk drive to utilize a device where a USB flash drive emulates the storage space of a floppy disk in a solid state form, and can be divided into a number of individual virtual floppy [[Disk image|disk image]]s using individual data channels.

===Optical media===
The various writable and re-writable forms of [[Engineering:CD|CD]] and [[Engineering:DVD|DVD]] are portable storage media supported by the vast majority of computers as of 2008. CD-R, DVD-R, and DVD+R can be written to only once, RW varieties up to about 1,000 erase/write cycles, while modern NAND-based flash drives often last for 500,000 or more erase/write cycles. [[Engineering:DVD-RAM|DVD-RAM]] discs are the most suitable optical discs for data storage involving much rewriting.

Optical storage devices are among the cheapest methods of mass data storage after the hard drive. They are slower than their flash-based counterparts. Standard 120&nbsp;mm optical discs are larger than flash drives and more subject to damage. Smaller optical media do exist, such as business card CD-Rs which have the same dimensions as a credit card, and the slightly less convenient but higher capacity 80&nbsp;mm recordable MiniCD and Mini DVD. The small discs are more expensive than the standard size, and do not work in all drives.

[[Universal Disk Format]] (UDF) version 1.50 and above has facilities to support rewritable discs like sparing tables and virtual [[File Allocation Table|allocation tables]], spreading usage over the entire surface of a disc and maximising life, but many older operating systems do not support this format. Packet-writing utilities such as DirectCD and [[Software:InCD|InCD]] are available but produce discs that are not universally readable (although based on the [[Universal Disk Format|UDF]] standard). The [[Mount Rainier (packet writing)|Mount Rainier]] standard addresses this shortcoming in CD-RW media by running the older file systems on top of it and performing defect management for those standards, but it requires support from both the CD/DVD burner and the [[Operating system|operating system]]. Many drives made today do not support Mount Rainier, and many older operating systems such as Windows XP and below, and Linux kernels older than 2.6.2, do not support it (later versions do). Essentially CDs/DVDs are a good way to record a great deal of information cheaply and have the advantage of being readable by most standalone players, but they are poor at making ongoing small changes to a large collection of information. Flash drives' ability to do this is their major advantage over optical media.

===Flash memory cards===
[[File:8GB media comparison.jpg|thumb|Three different [[Company:Micro Center|Micro Center]]-branded digital media, showing a USB flash drive, an SD card, and a Micro-SD card, all having a capacity of 8 GiB, next to a U.S 5-cent coin for size comparison]]
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.

Some manufacturers, aiming at a "best of both worlds" solution, have produced card readers that approach the size and form of USB flash drives (e.g., Kingston MobileLite,<ref>{{cite web|url=http://www.kingston.com/flash/mobilelite_reader.asp|title=MobileLite 9-in-1 Reader|publisher=Kingston Technology|access-date=2009-04-08|url-status=dead|archive-url=https://web.archive.org/web/20090227044548/http://kingston.com/flash/mobilelite_reader.asp|archive-date=2009-02-27}}</ref> [[Company:SanDisk|SanDisk]] MobileMate<ref>{{cite web |url=http://www.sandisk.com/Products/Item(1219)-SDDR-108-A11M-SanDisk_MobileMate_Memory_Stick_Plus_4in1_Reader.aspx |title=MobileMate Memory Stick Plus 4-in-1 Reader |publisher=[[Company:SanDisk|Sandisk Corporation]] |access-date=2009-04-08 |url-status=dead |archive-url=https://web.archive.org/web/20090305041708/http://www.sandisk.com/Products/Item%281219%29-SDDR-108-A11M-SanDisk_MobileMate_Memory_Stick_Plus_4in1_Reader.aspx |archive-date=March 5, 2009 }}</ref>)  These readers are limited to a specific subset of memory card formats (such as SD, [[Engineering:MicroSD|microSD]], or [[Memory Stick]]), and often completely enclose the card, offering durability and portability approaching, if not quite equal to, that of a flash drive. Although the combined cost of a mini-reader and a memory card is usually slightly higher than a USB flash drive of comparable capacity, the reader + card solution offers additional flexibility of use, and virtually "unlimited" capacity. The ubiquity of SD cards is such that, circa 2011, due to [[Finance:Economies of scale|economies of scale]], their price is now less than an equivalent-capacity USB flash drive, even with the added cost of a USB SD card reader.

An additional advantage of memory cards is that many consumer devices (e.g., [[Engineering:Digital camera|digital camera]]s, portable music players) cannot make use of USB flash drives (even if the device has a USB port), whereas the memory cards used by the devices can be read by PCs with a card reader.

===External hard disk===
Particularly with the advent of USB, external hard disks have become widely available and inexpensive. External hard disk drives currently cost less per gigabyte than flash drives and are available in larger capacities. Some hard drives support alternative and faster interfaces than USB 2.0 (e.g., [[Engineering:Thunderbolt (interface)|Thunderbolt]], [[Engineering:IEEE 1394|FireWire]] and eSATA). For consecutive sector writes and reads (for example, from an unfragmented file), most hard drives can provide a much higher sustained data rate than current NAND flash memory, though [[Engineering:Latency (engineering)#Mechanical latency|mechanical latencies]] seriously impact hard drive performance.

Unlike solid-state memory, hard drives are susceptible to damage by shock (e.g., a short fall) and vibration, have limitations on use at high altitude, and although they are shielded by their casings, they are vulnerable when exposed to strong magnetic fields. In terms of overall mass, hard drives are usually larger and heavier than flash drives; however, hard disks sometimes weigh less per unit of storage. Like flash drives, hard disks also suffer from file fragmentation, which can reduce access speed{{Citation needed|date=January 2022}}.

===Obsolete devices===
Audio tape cassettes and high-capacity floppy disks (e.g., Imation SuperDisk), and other forms of drives with removable magnetic media, such as the Iomega [[Engineering:Zip drive|Zip drive]] and [[Jaz drive]]s, are now largely obsolete and rarely used. There are products in today's market that will emulate these legacy drives for both tape and disk (SCSI1/SCSI2, SASI, Magneto optic, Ricoh ZIP, Jaz, IBM3590/ Fujitsu 3490E and Bernoulli for example) in state-of-the-art Compact Flash storage devices – CF2SCSI.

===Encryption and security===
{{main|Engineering:USB flash drive security}}

As highly portable media, USB flash drives are easily lost or stolen. All USB flash drives can have their contents encrypted using third-party disk encryption software, which can often be run directly from the USB drive without installation (for example, [[Software:FreeOTFE|FreeOTFE]]), although some, such as BitLocker, require the user to have administrative rights on every computer it is run on.

Archiving software can achieve a similar result by creating encrypted [[ZIP (file format)|ZIP]] or [[RAR (file format)|RAR]] files.<ref>{{cite web|url=https://www.pkware.com/software/pkzip/server/technical-specs|title=Technical Specifications - PKZIP Server - PKWARE - server - pkzip - software|author=Arlen Walker|work=pkware.com|access-date=29 June 2015}}</ref><ref>{{cite web|url=http://www.rarlab.com/rar_archiver.htm|title=WinRAR archiver, a powerful tool to process RAR and ZIP files|work=rarlab.com|access-date=29 June 2015}}</ref>

Some manufacturers have produced USB flash drives which use hardware-based encryption as part of the design,<ref name=hardware_encryption>{{cite web |url=http://www.goldkey.com/products/secure-encrypted-flash-drive.html |title=Encrypted & Secure USB Flash Drive - GoldKey |access-date=2016-02-09 |url-status=dead |archive-url=https://archive.today/20130124123810/http://www.goldkey.com/products/secure-encrypted-flash-drive.html |archive-date=2013-01-24 }}</ref> removing the need for third-party encryption software. In limited circumstances these drives have been [[Engineering:USB flash drive security#Compromised systems|shown to have security problems]], and are typically more expensive than software-based systems, which are available for free.

A minority of flash drives support biometric fingerprinting to confirm the user's identity. As of mid-{{As of|2005|alt=2005}},{{Update after|2010|11|13}} this was an expensive alternative to standard password protection offered on many new USB flash storage devices. Most fingerprint scanning drives rely upon the host operating system to validate the fingerprint via a software driver, often restricting the drive to [[Software:Microsoft Windows|Microsoft Windows]] computers. However, there are USB drives with fingerprint scanners which use controllers that allow access to protected data without any authentication.<ref>{{cite web|url=http://www.heise-online.co.uk/security/Secure-USB-sticks-cracked--/features/110280|title=heise online - IT-News, Nachrichten und Hintergründe|work=heise online}}</ref>

Some manufacturers deploy [[Engineering:Dongle|physical authentication tokens]] in the form of a flash drive. These are used to control access to a sensitive system by containing encryption keys or, more commonly, communicating with security software on the target machine. The system is designed so the target machine will not operate except when the flash drive device is plugged into it. Some of these "PC lock" devices also function as normal flash drives when plugged into other machines.

==Controversies==

===Criticisms===

====Failures====
Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before the drive fails.<ref>[http://www.bress.net/blog/archives/114-How-Long-Does-a-Flash-Drive-Last.html How Long Does a Flash Drive Last? – Josh's Blog] {{Webarchive|url=https://web.archive.org/web/20100213060937/http://www.bress.net/blog/archives/114-How-Long-Does-a-Flash-Drive-Last.html |date=2010-02-13 }}. 2008-05-23, Bress.net. Retrieved on 2011-05-18.</ref>{{Unreliable source?|date=December 2011}}<ref>{{Cite web|url=http://www.corsairmemory.com/_faq/FAQ_flash_drive_wear_leveling.pdf|archive-url=https://web.archive.org/web/20090206095926/http://www.corsairmemory.com/_faq/FAQ_flash_drive_wear_leveling.pdf|url-status=dead|title=What is flash drive wear leveling<!-- Bot generated title -->|archive-date=February 6, 2009}}</ref> This should be a consideration when using a flash drive to run application software or an operating system. To address this, as well as space limitations, some developers have produced special versions of operating systems (such as [[Software:Linux|Linux]] in [[Software:Live USB|Live USB]])<ref>[http://linux-usb.sourceforge.net/USB-guide/x498.html Mass Storage Devices]. Linux-usb.sourceforge.net. Retrieved on 2011-05-18.</ref> or commonplace applications (such as Mozilla Firefox) designed to run from flash drives. These are typically optimized for size and configured to place temporary or intermediate files in the computer's main RAM rather than store them temporarily on the flash drive.

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' [[Engineering:Failure of electronic components|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.<ref>{{cite web|last=Notenboom |first=Leo A. |url=http://ask-leo.com/how_do_i_fix_bad_sectors_on_a_flash_drive.html |title=How do I fix bad sectors on a flash drive? |website=Ask-leo.com |date=2008-05-06 |access-date=2017-06-06}}</ref>

Most USB flash drives do not include a [[Write protection|write protection]] mechanism. This feature, which gradually became less common, consists of a switch on the housing of the drive itself, that prevents the host computer from writing or modifying data on the drive.  For example, write protection makes a device suitable for repairing [[Computer virus|virus]]-contaminated host computers without the risk of infecting a USB flash drive itself.  In contrast to [[Engineering:SD card|SD card]]s, write protection on USB flash drives (when available) is connected to the drive circuitry, and is handled by the drive itself instead of the host (on SD cards handling of the write-protection notch is optional).

A drawback to the small physical size of flash drives is that they are easily misplaced or otherwise lost. This is a particular problem if they contain sensitive data (see [[Data security|data security]]). As a consequence, some manufacturers have added encryption hardware to their drives, although [[Software:Comparison of disk encryption software|software encryption systems]] which can be used in conjunction with any [[Mass storage|mass storage]] medium will achieve the same result. Most drives can be attached to keychains or lanyards. The USB plug is usually retractable or fitted with a removable protective cap.

====Robustness====
Most USB-based flash technology integrates a printed circuit board with a metal tip, which is simply soldered on. As a result, the stress point is where the two pieces join. The quality control of some manufacturers does not ensure a proper solder temperature, further weakening the stress point.<ref>[[Physics:Soldering#Electronics|Wikipedia entry "Soldering Defects in Electronics]]</ref><ref>Wikipedia entry "Processes – Electronic Components (PCBs)"</ref> Since many flash drives stick out from computers, they are likely to be bumped repeatedly and may break at the stress point. Most of the time, a break at the stress point tears the joint from the printed circuit board and results in permanent damage. However, some manufacturers produce discreet flash drives that do not stick out, and others use a solid metal or plastic uni-body that has no easily discernible stress point.  SD cards serve as a good alternative to USB drives since they can be inserted flush.

===Security threats===
====USB killer====
In appearance similar to a USB flash drive, a USB killer is a circuit that charges up [[Engineering:Capacitor|capacitor]]s to a high voltage using the power supply pins of a [[Engineering:USB#Connectors|USB port]] then discharges high voltage pulses onto the data pins. This completely standalone device can instantly and permanently damage or destroy any host hardware that it is connected to.<ref>{{cite web
 |url=https://www.pcworld.com/article/2896732/dont-trust-other-peoples-usb-flash-drives-they-could-fry-your-laptop.html
 |title=USB Killer is a flash drive designed to fry your laptop
 |last=Constantin
 |first=Lucian
 |date=Mar 13, 2015
 |website=PC World
 |access-date=May 2, 2018}}</ref>

==="Flash Drives for Freedom"===
The New York-based Human Rights Foundation collaborated with Forum 280 and USB Memory Direct to launch the "Flash Drives for Freedom" program.<ref>{{cite news |last1=Taggart |first1=Emma |title=You Can Donate Old USB Drives to These Activists to Help Free North Koreans of Propaganda |url=https://mymodernmet.com/north-korea-flash-drives-for-freedom/ |work=My Modern Met |access-date=10 January 2019 |language=en |date=22 August 2018}}</ref><ref>{{cite news |last1=Desreumaux |first1=Geoff |title=Flash Drives For Freedom: Your Old USB Drives Can Help Overthrow Dictatorships |url=https://wersm.com/flash-drives-for-freedom-your-old-usb-drives-can-help-overthrow-dictatorship/ |access-date=10 January 2019 |work=WeRSM - We are Social Media |date=23 August 2018}}</ref> The program was created in 2016 to smuggle flash drives with {{wipe|United States}} and {{wipe|South Korea}}n movies and television shows, as well as a copy of the Korean  Wikipedia, into North Korea to spread pro-Western sentiment.<ref name="theguardianflashdrivesforfreedom">{{cite news|last1=Hands|first1=Jack|title=Flashdrives for freedom? 20,000 USBs to be smuggled into North Korea|url=https://www.theguardian.com/world/2016/mar/22/flashdrives-for-freedom-north-korea-20000-usb-sticks|access-date=March 18, 2017|work=The Guardian|date=March 22, 2016}}</ref><ref name="reasonhowactivistsareusing">{{cite web|last1=Bragg|first1=Austin|last2=Bragg|first2=Meredith|last3=Detrick|first3=Paul|title=#SXSW: How Activists Are Using Technology to Fight Dictators|url=https://reason.com/reasontv/2017/03/15/sxsw-how-activists-are-using-technology|website=Reason Foundation|access-date=March 18, 2017|date=March 15, 2017}}</ref>

==Current and future developments==
[[File:USB 3.0 Flash Drive PCB.jpg|thumb|The internals of a 32&nbsp;GB [[Company:Toshiba|Toshiba]] USB 3.0 flash drive. The USB 3.0 standard is becoming increasingly popular. This drive has a write speed of 60&nbsp;MB/s and a read speed of 120&nbsp;MB/s, making it faster than the USB 2.0 standard.]]

Semiconductor corporations have worked to reduce the cost of the components in a flash drive by integrating various flash drive functions in a single chip, thereby reducing the part-count and overall package-cost.

Flash drive capacities on the market increase continually. High speed has become a standard for modern flash drives. Capacities exceeding 256&nbsp;GB were available on the market as early as 2009.<ref name="Kingston256GB"/>

[[Company:Lexar|Lexar]] is attempting to introduce a ''[[Engineering:USB FlashCard|USB FlashCard]]'', which would be a compact USB flash drive intended to replace various kinds of flash memory cards. Pretec introduced a similar card, which also plugs into any USB port, but is just one quarter the thickness of the Lexar model.<ref name=pretec>{{cite web|url=http://www.pretec.com/epages/Store.storefront/?ObjectPath=/Shops/Store.Pretec/Products/Q2UXXX|title=Pretec - Small size, Big impact|last=Administrator|access-date=1 June 2016}}</ref> Until 2008, SanDisk manufactured a product called SD Plus, which was a SecureDigital card with a USB connector.<ref>{{cite web|url=http://www.dpreview.com/news/0501/05010606sandisksdflip.asp|title=SanDisk Ultra II SD Plus Cards|publisher=SanDisk|access-date=2008-03-02}}</ref>

SanDisk has also introduced a new technology to allow controlled storage and usage of copyrighted materials on flash drives, primarily for use by students. This technology is termed FlashCP.

==See also==

{{Div col|colwidth=20em}}
* List of computer hardware
* [[Engineering:Memristor|Memristor]]
* [[Microdrive]]
* [[Nonvolatile BIOS memory]]
* [[Software:Portable application|Portable application]]
* [[Software:ReadyBoost|ReadyBoost]]
* [[Sneakernet]]
* [[Solid-state drive]] (SSD)
* [[Engineering:USB dead drop|USB dead drop]]
* [[Organization:USB Flash Drive Alliance|USB Flash Drive Alliance]]
* [[Software:Windows To Go|Windows To Go]]
* [[Disk enclosure]]
* [[External storage]]
* [[Engineering:BadUSB|BadUSB]]
{{Div col end}}

==Notes==
<!--Notes list-->
{{Reflist|group=note}}

==References==
{{Reflist}}

{{Basic computer components}}

[[Category:Solid-state computer storage]]
[[Category:Office equipment]]

{{Sourceattribution|USB flash drive|1}}