Editing SD card

{{Short description|Type of memory storage for portable devices}}
{{Redirect|SDHC|the gene|SDHC (gene)}}
{{See also|Comparison of memory cards}}
{{For|the earlier form|MultiMediaCard}}
{{use dmy dates|date=October 2024}}
{{Infobox storage medium
| name = Secure Digital (SD)
| logo = [[File:SD-Logo.svg|frameless|upright=0.5|class=skin-invert]]
| image = SD Cards.svg
| caption = From top to bottom: SD, miniSD, microSD
| type = [[Memory card]]
| capacity = {{ubli
 | '''SD''': Up to {{Nowrap|2 GB}}
 | '''SDHC''': Up to {{Nowrap|32 GB}}
 | '''SDXC''': Up to {{Nowrap|2 TB}}
 | '''SDUC''': Up to {{Nowrap|128 TB}}
 }}
| blocksize = Variable
| read = {{ubli
 | '''Default''': 12.5&nbsp;MB/s
 | '''High-speed''': 25&nbsp;MB/s
 | '''UHS-I''': 52&nbsp;MB/s (SDR50, DDR50) or 104&nbsp;MB/s (SDR104)
 | '''UHS-II''': 156&nbsp;MB/s full-duplex or 312&nbsp;MB/s half-duplex
 | '''UHS-III''': 312&nbsp;MB/s full-duplex or 624&nbsp;MB/s half-duplex
 | '''Express''': Up to 3,940&nbsp;MB/s
 }}
| owner = [[SD Association]]
| dimensions = {{Unbulleted list
  | '''Standard''':
  | {{cvt|32|*|24|*|2.1|mm}}
  | {{cvt|1612.8|mm3}}
  | '''Mini''':
  | {{cvt|21.5|*|20|*|1.4|mm}}
  | {{cvt|602|mm3}}
  | '''Micro''':
  | {{cvt|15|*|11|*|1|mm}}
  | {{cvt|165|mm3}}
  }}
| weight = {{Unbulleted list
 | '''Standard''': {{Nowrap|~2 [[Gram|g]]}}
 | '''Mini''': {{Nowrap|~0.8 g}}
 | '''Micro''': {{Nowrap|~0.25 g}}
 }}
| extended from = [[MultiMediaCard]]
| extended to = 
| released = August 1999
| discontinued = 
}}

'''Secure Digital (SD)''' is a [[proprietary hardware|proprietary]], [[non-volatile memory|non-volatile]], [[flash memory]] card format developed by the [[SD Association]] (SDA). Owing to their compact size, SD cards have been widely adopted in a variety of portable consumer electronics, including [[digital camera]]s, [[camcorder]]s, [[video game console]]s, [[mobile phone]]s, [[action camera]]s, and [[Unmanned aerial vehicle|camera drones]].<ref name="FB" /><ref name="AD" />

The SD format was introduced in August 1999 by [[SanDisk]], [[Panasonic]] (then known as Matsushita), and [[Kioxia]] (then part of [[Toshiba]]). It was designed as a successor to the [[MultiMediaCard]] (MMC) format, introducing several improvements aimed at enhancing usability, durability, and performance, which contributed to its rapid emergence as an industry standard.

To manage the licensing and intellectual property rights related to the format, the three companies established SD-3C, LLC. In January 2000, they also founded the SDA, a non-profit organization dedicated to developing and promoting SD card standards.<ref name="SD Association">{{cite web |date=2015-03-30 |title=Matsushita Electric, SanDisk and Toshiba to Form SD Association to Promote Next Generation SD Memory Card |url=https://www.toshiba.co.jp/about/press/2000_01/pr0602.htm |url-status=live |archive-url=https://web.archive.org/web/20190101010324/https://www.toshiba.co.jp/about/press/2000_01/pr0602.htm |archive-date=2019-01-01 |access-date=2016-02-23 |publisher=Toshiba}}</ref> As of 2023, the SDA includes approximately 1,000 member companies. The SDA uses a suite of SD-3C-owned trademarked logos to enforce compliance with official specifications and to indicate product compatibility.<ref>{{cite web |date=2010-06-22 |title=Using SD Memory Cards is Easy |url=https://www.youtube.com/watch?v=wX6NwBa1csY |archive-url=https://ghostarchive.org/varchive/youtube/20211029/wX6NwBa1csY |archive-date=2021-10-29 |access-date=2014-01-02 |publisher=SD Association}}{{cbignore}}</ref>

== History ==

=== 1999–2005: Creation and introduction of smaller formats ===
In 1999, [[SanDisk]], [[Panasonic]] (then known as Matsushita), and [[Kioxia]] (then part of [[Toshiba]]) agreed to develop and market the Secure Digital (SD) memory card.<ref>{{cite web|url=http://www.dpreview.com/articles/6861681955/newmemory|title=Three Giants to develop new "Secure Memory Card"|publisher=DP review|access-date=2016-02-23|archive-date=2019-09-04|archive-url=https://web.archive.org/web/20190904031748/http://www.dpreview.com/articles/6861681955/newmemory|url-status=live}}</ref><ref name="partnership">{{cite web |date=1999-08-24 |title=Matsushita Electric, SanDisk and Toshiba Agree to Join Forces to Develop and Promote Next Generation Secure Memory Card |url=http://www.dpreview.com/articles/6861681955/newmemory |url-status=live |archive-url=https://web.archive.org/web/20190904031748/http://www.dpreview.com/articles/6861681955/newmemory |archive-date=2019-09-04 |access-date=2016-02-23 |publisher=DP Review}}</ref> The card was created as a second-generation successor to the [[MultiMediaCard]] (MMC)<ref>{{Cite web |last=Andrews |first=Ben |date=2022-10-25 |title=Flash back: the history of the SD card, and why we think it deserves more love |url=https://www.digitalcameraworld.com/features/flash-back-the-history-of-the-sd-card-and-why-we-think-it-deserves-more-love |access-date=2024-06-19 |website=Digital Photography Review}}</ref> and provided [[digital rights management]] (DRM) based on the [[Secure Digital Music Initiative]] (SDMI) standard and a high [[memory density]] ("data/bits per physical space"), i.e. a large quantity of data could be stored in a small physical space.{{citation needed|date=September 2023}}

SD was designed to compete with the [[Memory Stick]], a flash storage format with DRM [[Sony]] had released the year before. Toshiba hoped the SD card's DRM would encourage music suppliers concerned about piracy to use SD cards.<ref>{{cite web|url=http://www.toshiba.co.jp/about/press/2003_07/pr1701.htm|title=Press Releases 17 July 2003|publisher=Toshiba|date=2003-07-17|access-date=2010-08-22|archive-date=2010-09-08|archive-url=https://web.archive.org/web/20100908075309/http://www.toshiba.co.jp/about/press/2003_07/pr1701.htm|url-status=live}}</ref>

The trademarked SD logo was originally developed for the [[Super Density Disc]], which was the unsuccessful Toshiba entry in the [[DVD]] format war. For this reason, the letter "D" is styled to resemble an optical disc.<ref>{{Citation |title=The Odd History of the SD Logo | date=21 January 2019 |url=https://www.youtube.com/watch?v=VeLvdE8lNW4 |access-date=2023-10-25 |language=en}}</ref>

At the 2000 [[Consumer Electronics Show]] (CES), the three companies announced the creation of the [[SD Association]] (SDA) to promote SD cards. The SD Association, which was headquartered in [[San Ramon, California]], United States, then had 30 member companies and product manufacturers that made interoperable memory cards and devices. Early samples of the SD card<ref>{{cite web |url=https://www.bitwarsoft.com/what-is-an-sd-card.html |title=What is SD Card |publisher=Bitwarsoft.com |date=2020-07-24 |access-date=2021-06-30 |archive-date=2021-07-09 |archive-url=https://web.archive.org/web/20210709181808/https://www.bitwarsoft.com/what-is-an-sd-card.html |url-status=live }}</ref> became available in the first quarter of 2000, and production quantities of 32 and 64 [[megabyte]] (MB){{efn|except where indicated otherwise, 1&nbsp;MB equals one million bytes}} cards became available three months later.{{citation needed|date=September 2023}}<!-- found source? <ref>https://www.global.toshiba/ww/news/corporate/2000/01/pr0602.html {{Bare URL inline|date=August 2024}}</ref>--> The first 64&nbsp;MB cards were offered for sale for US$200.<ref>{{Cite web|url=https://books.google.com/books?id=xA5vzkW8IDsC&dq=64mb+sd+card+second+quarter+2000&pg=PA40|title=Popular Science|first=Bonnier|last=Corporation|date=August 27, 2000|publisher=Bonnier Corporation|via=Google Books}}</ref> SD was envisioned as a single memory card format for several kinds of electronic devices that could also function as an expansion slot for adding new capabilities for a device.<ref>{{Cite web|url=https://books.google.com/books?id=VW7ZIgUJwSMC&dq=64mb+sd+card+second+quarter+2000&pg=PA90|title=Popular Science|first=Bonnier|last=Corporation|date=May 27, 2000|publisher=Bonnier Corporation|via=Google Books}}</ref> The first 256&nbsp;MB and 512&nbsp;MB SD cards were announced in 2001.<ref>{{cite web | url=https://m.dpreview.com/articles/9501387485/sdmmc256mb512mb | title=256 and 512 MB MMC / SD cards }}</ref>

==== miniSD ====
[[File:MiniSD memory card including adapter.jpg|thumb|MiniSD memory card including adapter]]

At March 2003 [[CeBIT]], SanDisk Corporation introduced, announced and demonstrated the '''miniSD''' form factor.<ref name="miniSD_announcement">[http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=1536 SanDisk Introduces The World's Smallest Removable Flash Card For Mobile Phones-The miniSD Card] {{Webarchive|url=https://web.archive.org/web/20090114232017/http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=1536 |date=2009-01-14 }} SanDisk.com</ref> The SDA adopted the miniSD card in 2003 as a small-form-factor extension to the SD card standard. While the new cards were designed for mobile phones, they were usually packaged with a miniSD adapter that provided compatibility with a standard SD memory card slot.{{citation needed|date=September 2023}}

==== microSD ====
[[File:Samsung Galaxy A02s microSD slot.JPG|thumb|microSD card inserted on a [[smartphone]]]]
'''MicroSD''' form-factor memory cards were introduced in 2004 by SanDisk at CeBIT<ref>{{Cite web|url=https://www.itmedia.co.jp/news/articles/0403/22/news002.html|title=HD録画のカムコーダ、DVD-R内蔵ミニノート……会場で見かけた新製品|date=March 22, 2004|website=ITmedia NEWS|access-date=February 12, 2024|archive-date=September 11, 2024|archive-url=https://web.archive.org/web/20240911012959/https://www.itmedia.co.jp/news/articles/0403/22/news002.html|url-status=live}}</ref> and originally called T-Flash,<ref>{{cite news |title=T-Flash: aka 'Yet Another Memory Card Format' |first=Peter |last=Rojas |date=2 March 2004 |journal=[[Engadget]] |url=https://www.engadget.com/2004/03/02/t-flash-aka-yet-another-memory-card-format/ |access-date=2 May 2019 |archive-date=2 May 2019 |archive-url=https://web.archive.org/web/20190502064324/https://www.engadget.com/2004/03/02/t-flash-aka-yet-another-memory-card-format/ |url-status=live }}</ref> and later TransFlash,<ref>{{Cite web |date=24 May 2004 |title=SanDisk releases new memory cards |url=https://www.cnet.com/tech/tech-industry/sandisk-releases-new-memory-cards/ |url-status=live |archive-url=https://web.archive.org/web/20240222023250/https://www.cnet.com/tech/tech-industry/sandisk-releases-new-memory-cards/ |archive-date=2024-02-22 |access-date=2024-02-12 |website=CNET}}</ref> commonly abbreviated to "TF". T-Flash was renamed microSD in 2005 when it was adopted by the SDA.<ref>
{{cite web | url=https://www.theregister.com/2005/07/14/transflash_is_microsd/ | title=TransFlash becomes MicroSD | access-date=2024-02-03 | archive-date=2024-09-11 | archive-url=https://web.archive.org/web/20240911012959/https://www.theregister.com/2005/07/14/transflash_is_microsd/ | url-status=live }}
</ref> TransFlash and microSD cards are functionally identical, allowing either to operate in devices made for the other.<ref name="Phonescoop">{{cite web |url=https://www.phonescoop.com/articles/article.php?a=801 |title=SanDisk Reveals Tiny New Memory Cards for Phones |publisher=Phonescoop.com |date=28 February 2004 |access-date=2014-01-02 |archive-date=2012-07-22 |archive-url=https://web.archive.org/web/20120722005048/http://www.phonescoop.com/articles/article.php?a=801 |url-status=live }}</ref> A passive adapter allows the use of microSD and TransFlash cards in SD card slots.<ref name="Phonescoop"/><ref>{{Cite web|url=https://ko.com.ua/cebit_2004_nastraivaemsya_na_volnu_budushhego_16835|title=CeBIT 2004: "Настраиваемся на волну будущего" &#124; Статьи &#124; Компьютерное Обозрение|website=ko.com.ua|access-date=2024-02-12|archive-date=2024-09-11|archive-url=https://web.archive.org/web/20240911013022/https://ko.com.ua/cebit_2004_nastraivaemsya_na_volnu_budushhego_16835|url-status=live}}</ref>

=== 2006–2008: SDHC and SDIO ===
[[File:8 bytes vs. 8Gbytes.jpg|thumb|This microSDHC card holds 8 billion bytes. Beneath it is a section of a [[magnetic-core memory]] (used until the 1970s) that holds eight bytes using 64 cores. The card covers approximately 20 bits ({{frac|2|1|2}} bytes).]]

In September 2006, SanDisk announced the 4&nbsp;GB miniSDHC.<ref name="miniSDHC_announcement">[http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=3530 SanDisk Introduces 4&nbsp;GB miniSDHC Flash Card for Mobile Phones] {{Webarchive|url=https://web.archive.org/web/20090115110619/http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=3530 |date=2009-01-15 }} SanDisk.com</ref> Like the SD and SDHC, the miniSDHC card has the same form factor as the older miniSD card but the HC card requires HC support built into the host device.{{citation needed|date=September 2023}} Devices that support miniSDHC work with miniSD and miniSDHC, but devices without specific support for miniSDHC work only with the older miniSD card. Since 2008, miniSD cards are no longer produced, due to market domination of the even smaller microSD cards.{{citation needed|date=September 2023}}

=== 2009–2019: SDXC ===
[[File:MicroSDXC.64GB.P1127589.jpg|thumb|right|Macro shot of a microSDXC memory card with eight gold plated electrical contacts]]

The storage density of memory cards increased significantly{{quantify|by how much?|date=June 2023}} throughout the 2010s, allowing the earliest devices to offer support for the SD:XC standard, such as the [[Samsung Galaxy S III]] and [[Samsung Galaxy Note II]] mobile phones, to expand their available storage to several hundreds of [[gigabyte]]s.

In January 2009, the SDA announced the SDXC family, which supports cards up to 2&nbsp;TB{{efn|name="here, 1&nbsp;TB = 1024"|reference=here, 1&nbsp;TB = 1024<sup>4</sup> B}} and speeds up to 300&nbsp;MB/s.<ref>{{cite web |title=SDXC SIGNALS NEW GENERATION OF REMOVABLE MEMORY WITH UP TO 2 TERABYTES OF STORAGE |url=https://www.sdcard.org/cms/wp-content/uploads/2020/11/SD_Association_Announces_SDXC_Revised_1-7-09.pdf |website=sdcard.org |publisher=SD Association |access-date=30 December 2023 |archive-date=11 September 2024 |archive-url=https://web.archive.org/web/20240911012842/https://www.sdcard.org/cms/wp-content/uploads/2020/11/SD_Association_Announces_SDXC_Revised_1-7-09.pdf |url-status=live }}</ref> SDXC cards are formatted with the [[exFAT]] file system by default.<ref>{{Cite web |date=2020-12-11 |title=Capacity (SD/SDHC/SDXC/SDUC) {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |access-date=2022-03-08 |website=sdcard.org |language=en-US |archive-date=2022-03-08 |archive-url=https://web.archive.org/web/20220308120216/https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |url-status=live}}</ref> SDXC was announced at the [[Consumer Electronics Show]] (CES) 2009 (January 7–10). At the same show, [[SanDisk]] and [[Sony]] also announced a comparable [[Memory Stick XC]] variant with the same 2&nbsp;TB{{efn|name="here, 1&nbsp;TB = 1024"}} maximum as SDXC,<ref>{{cite web |url= http://www.sandisk.com/about-sandisk/press-room/press-releases/2009/2009-01-07-sandisk-and-sony-to-expand-%E2%80%9Cmemory-stick-pro%E2%80%9D-and-%E2%80%9Cmemory-stick-micro%E2%80%9D-formats |title= SanDisk and Sony to expand Memory Stick Pro and Memory Stick Micro formats |publisher= SanDisk |date= 2009-01-07 |access-date= 2010-08-22 |archive-date= 2010-01-07 |archive-url= https://web.archive.org/web/20100107054251/http://www.sandisk.com/about-sandisk/press-room/press-releases/2009/2009-01-07-sandisk-and-sony-to-expand-%E2%80%9Cmemory-stick-pro%E2%80%9D-and-%E2%80%9Cmemory-stick-micro%E2%80%9D-formats |url-status= live}}</ref> and [[Panasonic]] announced plans to produce 64&nbsp;GB SDXC cards.<ref name="betanews_2t_sdxc">{{cite web |last=Mook |first=Nate |date=2009-01-08 |title=SD Card, Memory Stick formats to reach 2 terabytes, but when? |url=https://betanews.com/2009/01/08/sd-card-memory-stick-formats-to-reach-2-terabytes-but-when |access-date=2024-01-22 |work=Beta news |archive-date=2024-03-09 |archive-url=https://web.archive.org/web/20240309234452/https://betanews.com/2009/01/08/sd-card-memory-stick-formats-to-reach-2-terabytes-but-when/ |url-status=live}}</ref> On March 6, Pretec introduced the first SDXC card,<ref name="dpreview pretec sdxc">{{cite web |url=http://www.dpreview.com/news/0903/09030601pretecsdxc.asp |title= Pretec introduces world's first SDXC card |work= Digital Photography Review |date= 2009-03-06 |access-date= 2010-08-22 |archive-date= 2010-08-21 |archive-url= https://web.archive.org/web/20100821022647/http://www.dpreview.com/news/0903/09030601pretecsdxc.asp |url-status= live}}</ref> a 32&nbsp;GB card with a read/write speed of 400&nbsp;Mbit/s. But only early in 2010 did compatible host devices come onto the market, including [[Sony]]'s [[Handycam]] HDR-CX55V [[camcorder]], [[Canon (company)|Canon]]'s [[Canon EOS 550D|EOS 550D]] (also known as Rebel T2i) Digital SLR camera,<ref name="The-Digital-Picture.com-T2i_500D">{{cite web| title= Canon EOS Rebel T2i/550D Digital SLR Camera Review| url= http://www.the-digital-picture.com/Press-Release/Canon-EOS-Rebel-T2i-550D-Digital-SLR-Camera-Press-Release.aspx| publisher= The Digital Picture| access-date= 2010-02-09| archive-date= 2010-02-11| archive-url= https://web.archive.org/web/20100211220305/http://www.the-digital-picture.com/Press-Release/Canon-EOS-Rebel-T2i-550D-Digital-SLR-Camera-Press-Release.aspx| url-status= live}}</ref> a USB card reader from Panasonic, and an integrated SDXC card reader from JMicron.<ref name="JMicron">{{cite web |url=http://www.dailytech.com/Lack+of+Card+Readers+Holding+Back+SDXC+Flash+Memory+Adoption/article16915.htm |title=Lack of Card Readers Holding Back SDXC Flash Memory Adoption |access-date=2009-12-22 |last=Ng |first=Jansen |date=2009-11-24 |publisher=[[DailyTech]] |archive-date=2007-06-11 |archive-url=https://web.archive.org/web/20070611074105/http://www.dailytech.com/ |url-status=dead}}</ref> The earliest laptops to integrate SDXC card readers relied on a USB 2.0 bus, which does not have the bandwidth to support SDXC at full speed.<ref name="Laptops">{{cite web |url=http://www.dailytech.com/Lenovo+HP+Dell+Integrating+SDXC+Readers+in+New+32nm+Intel+Arrandale+Laptops/article16937.htm |title=Lenovo, HP, Dell Integrating SDXC Readers in New 32nm Intel "Arrandale" Laptops |access-date=2009-12-22 |last=Ng |first=Jansen |date=2009-11-30 |publisher=[[DailyTech]] |archive-date=2015-01-01 |archive-url=https://web.archive.org/web/20150101030411/http://www.dailytech.com/Lenovo+HP+Dell+Integrating+SDXC+Readers+in+New+32nm+Intel+Arrandale+Laptops/article16937.htm |url-status=dead}}</ref>

In early 2010, commercial SDXC cards appeared from [[Toshiba]] (64&nbsp;GB),<ref name="DailyTech">{{cite web |url=http://www.dailytech.com/Toshiba+Sampling+First+SDXC+Flash+Memory+Cards/article16972.htm |title=Toshiba Sampling First SDXC Flash Memory Cards |access-date=2009-12-22 |last=Ng |first=Jansen |date=2009-12-22 |publisher=[[DailyTech]] |archive-date=2010-11-25 |archive-url=https://web.archive.org/web/20101125031137/http://www.dailytech.com/Toshiba+Sampling+First+SDXC+Flash+Memory+Cards/article16972.htm |url-status=dead}}</ref><ref name="CrunchGear">{{cite web |url=http://www.crunchgear.com/2010/04/15/toshibas-64gb-sdxc-card-to-finally-go-on-sale-in-japan/ |title=Toshiba's 64&nbsp;GB SDXC card to finally go on sale (in Japan) |access-date=2010-08-09 |publisher=[[CrunchGear]] |archive-date=2010-07-01 |archive-url=https://web.archive.org/web/20100701214307/http://www.crunchgear.com/2010/04/15/toshibas-64gb-sdxc-card-to-finally-go-on-sale-in-japan/ |url-status=dead}}</ref> Panasonic (64&nbsp;GB and 48&nbsp;GB),<ref name="Panasonic">{{cite web |url=http://www2.panasonic.com/webapp/wcs/stores/servlet/prModelDetail?storeId=11301&catalogId=13251&itemId=389511&modelNo=Content01052010041118461&surfModel=Content01052010041118461 |title=Panasonic Introduces New 64&nbsp;GB* and 48&nbsp;GB* SDXC Memory Cards, Available Globally in February 2010 |access-date=2010-08-09 |publisher=[[Panasonic]] |archive-date=2010-04-21 |archive-url=https://web.archive.org/web/20100421194326/http://www2.panasonic.com/webapp/wcs/stores/servlet/prModelDetail?storeId=11301&catalogId=13251&itemId=389511&modelNo=Content01052010041118461&surfModel=Content01052010041118461 |url-status=dead}}</ref> and SanDisk (64&nbsp;GB).<ref name="SanDisk">{{cite web |date=2010-02-22 |url=http://sandisk.com/about-sandisk/press-room/press-releases/2010/2010-02-22-sandisk-ships-its-highest-capacity-sd-card-ever,-the-64gb-sandisk-ultra-sdxc-card |title=Sandisk ships its highest capacity sd card ever |access-date=2010-08-09 |publisher=[[SanDisk]] |archive-date=2011-11-13 |archive-url=https://web.archive.org/web/20111113193538/http://sandisk.com/about-sandisk/press-room/press-releases/2010/2010-02-22-sandisk-ships-its-highest-capacity-sd-card-ever,-the-64gb-sandisk-ultra-sdxc-card |url-status=dead}}</ref>

In early 2011, [[Centon Electronics, Inc.]] (64&nbsp;GB and 128&nbsp;GB) and [[Lexar]] (128&nbsp;GB) began shipping SDXC cards rated at Speed Class 10.<ref>{{cite web |last=Conneally |first=Tim |date=2011-03-16 |title=Lexar ships 128 GB Class 10 SDXC card; March 2011 |url=https://betanews.com/2011/03/16/lexar-ships-first-128gb-sdxc-cards |access-date=2024-01-22 |publisher=Betanews.com |archive-date=2023-11-11 |archive-url=https://web.archive.org/web/20231111195250/https://betanews.com/2011/03/16/lexar-ships-first-128gb-sdxc-cards/ |url-status=live}}</ref> Pretec offered cards from 8&nbsp;GB to 128&nbsp;GB rated at Speed Class 16.<ref>{{cite web |url=http://www.pretec.com/news-event/press-room/item/root/sdxcsdhc-433x-c16 |title=SDXC/SDHC 433X Class 16 Card from Pretec |publisher=Pretec |date=2011-06-13 |access-date=2010-12-03 |archive-date=2011-11-29 |archive-url=https://web.archive.org/web/20111129134013/http://www.pretec.com/news-event/press-room/item/root/sdxcsdhc-433x-c16 |url-status=live}}</ref> In September 2011, SanDisk released a 64&nbsp;GB microSDXC card.<ref>{{Citation |url=http://pocketnow.com/smartphone-news/first-64gb-microsd-card-arrives-when-will-smartphones-support |title=First 64GB microSD Card Here; When Will Smartphones Support It? |newspaper=Pocket now |date=7 October 2017 |access-date=4 October 2011 |archive-date=11 October 2011 |archive-url=https://web.archive.org/web/20111011085002/http://pocketnow.com/smartphone-news/first-64gb-microsd-card-arrives-when-will-smartphones-support |url-status=dead}}</ref> Kingmax released a comparable product in 2011.<ref>{{Citation |url=https://www.engadget.com/2011/05/26/kingmax-flaunts-worlds-first-64gb-microsd-card/ |title=Kingmax flaunts world's first 64&nbsp;GB microSD card |newspaper=Engadget |date=2011-05-26 |access-date=2024-09-11 |archive-date=2017-06-25 |archive-url=https://web.archive.org/web/20170625180558/https://www.engadget.com/2011/05/26/kingmax-flaunts-worlds-first-64gb-microsd-card/ |url-status=live}}</ref>

In April 2012, Panasonic introduced [[MicroP2]] card format for professional video applications. The cards are essentially full-size SDHC or SDXC UHS-II cards, rated at UHS Speed Class U1.<ref name="www2.panasonic.com">{{cite web |url=http://www2.panasonic.com/webapp/wcs/stores/servlet/prModelDetail?storeId=11301&catalogId=13251&itemId=696010&modelNo=Content03202013033731832&surfModel=Content03202013033731832 |title=For Journalists |publisher=.panasonic.com |date=2013-03-20 |access-date=2014-01-02 |url-status=dead |archive-url=https://web.archive.org/web/20130526104856/http://www2.panasonic.com/webapp/wcs/stores/servlet/prModelDetail?storeId=11301&catalogId=13251&itemId=696010&modelNo=Content03202013033731832&surfModel=Content03202013033731832 |archive-date=2013-05-26}}</ref><ref>{{cite web |url=http://pro-av.panasonic.net/en/sales_o/p2/microP2/ |title=microP2 Card {{pipe}} P2 Series {{pipe}} Broadcast and Professional AV |publisher=Pro-av.panasonic.net |access-date=2014-01-02 |archive-date=2014-01-07 |archive-url=https://web.archive.org/web/20140107220225/http://pro-av.panasonic.net/en/sales_o/p2/microP2/ |url-status=live}}</ref> An adapter allows MicroP2 cards to work in current [[P2 (storage media)|P2 card]] equipment.<ref>{{cite web |last=Lawler |first=Richard |url=https://www.engadget.com/2012/04/15/panasonic-introduces-new-microp2-sd-sized-storage-at-nab-2012/ |title=Panasonic introduces new microP2 SD-sized storage at NAB 2012 |publisher=Engadget.com |date=2012-04-15 |access-date=2014-01-02 |archive-date=2013-12-19 |archive-url=https://web.archive.org/web/20131219022107/http://www.engadget.com/2012/04/15/panasonic-introduces-new-microp2-sd-sized-storage-at-nab-2012/ |url-status=live}}</ref>

Panasonic MicroP2 cards shipped in March 2013 and were the first UHS-II compliant products on market; initial offer includes a 32&nbsp;GB SDHC card and a 64&nbsp;GB SDXC card.<ref name="www2.panasonic.com"/><ref>{{cite web |last=Renée |first=V |url=http://nofilmschool.com/2013/03/panasonic-microp2-card-april-release/ |title=Panasonic's New Smaller, Faster, and Lower-Cost MicroP2 Cards Coming in April, Starting at $250 « No Film School |date=23 March 2013 |publisher=Nofilmschool.com |access-date=2014-01-02 |archive-date=2013-12-29 |archive-url=https://web.archive.org/web/20131229102628/http://nofilmschool.com/2013/03/panasonic-microp2-card-april-release/ |url-status=live}}</ref> Later that year, Lexar released the first 256&nbsp;GB SDXC card, based on 20&nbsp;nm [[NAND flash]] technology.<ref>{{cite web|title=Lexar Announces Industry's First 256&nbsp;GB SDXC UHS-I Memory Card|url=http://www.lexar.com/about/newsroom/press-releases/lexar-announces-industry-s-first-256gb-sdxc-uhs-i-memory-card|publisher=Micron|access-date=22 December 2012|archive-date=29 January 2013|archive-url=https://web.archive.org/web/20130129122438/http://www.lexar.com/about/newsroom/press-releases/lexar-announces-industry-s-first-256gb-sdxc-uhs-i-memory-card|url-status=live}}</ref>

In February 2014, SanDisk introduced the first 128&nbsp;GB microSDXC card,<ref>{{cite web|url=http://www.sandisk.com/about-sandisk/press-room/press-releases/2014/sandisk-introduces-worlds-highest-capacity-microsdxc-memory-card-at-128&nbsp;gb/|title=SANDISK INTRODUCES WORLD'S HIGHEST CAPACITY microSDXC MEMORY CARD AT 128GB|last=SanDisk|website=sandisk.com}}</ref> which was followed by a 200&nbsp;GB microSDXC card in March 2015.<ref>{{Cite web |url=http://www.sandisk.com/about-sandisk/press-room/press-releases/2015/200gb-sandisk-ultra-microsdxc-uhs-i-card-premium-edition/ |publisher=SanDisk.com |title=SanDisk introduces the first 200GB microSDXC card |date=2014-02-24 |access-date=2016-06-06 |archive-date=2015-09-01 |archive-url=https://web.archive.org/web/20150901074355/http://www.sandisk.com/about-sandisk/press-room/press-releases/2015/200gb-sandisk-ultra-microsdxc-uhs-i-card-premium-edition/ |url-status=live}}</ref> September 2014 saw SanDisk announce the first 512&nbsp;GB SDXC card.<ref>{{Cite web|url=https://www.sandisk.com/about/media-center/press-releases/2014/sandisk-premieres-worlds-highest-capacity-sd-card-for-high-performance-video-and-photo-capture|title=SanDisk Premieres World's Highest Capacity SD Card for High Performance Video and Photo Capture|last=SanDisk|website=sandisk.com|access-date=2016-09-20|archive-date=2017-01-18|archive-url=https://web.archive.org/web/20170118081201/https://www.sandisk.com/about/media-center/press-releases/2014/sandisk-premieres-worlds-highest-capacity-sd-card-for-high-performance-video-and-photo-capture|url-status=live}}</ref>

Samsung announced the world's first EVO Plus 256&nbsp;GB microSDXC card in May 2016,<ref>{{Cite web |url=https://news.samsung.com/global/samsung-electronics-introduces-the-evo-plus-256gb-microsd-card-with-the-highest-capacity-in-its-class |publisher=news.samsung.com |title=Samsung Electronics Introduces the EVO Plus 256 GB MicroSD Card, with the Highest Capacity in its Class |date=2016-05-10 |access-date=2016-06-06 |archive-date=2016-08-08 |archive-url=https://web.archive.org/web/20160808115631/https://news.samsung.com/global/samsung-electronics-introduces-the-evo-plus-256gb-microsd-card-with-the-highest-capacity-in-its-class |url-status=live}}</ref> and in September 2016 [[Western Digital]] (SanDisk) announced that a prototype of the first 1&nbsp;TB{{efn|reference=except where stated otherwise, in this article 1&nbsp;TB = 1000 billion bytes}} SDXC card would be demonstrated at [[Photokina]].<ref>{{Cite web|url=https://www.sandisk.com/about/media-center/press-releases/2016/western-digital-demonstrates-prototype-of-the-worlds-first-1terabyte-SDXC-card|title=Western Digital Demonstrates Prototype of the World's First 1Terabyte SDXC Card|last=SanDisk|website=sandisk.com|access-date=2016-09-20|archive-date=2017-01-18|archive-url=https://web.archive.org/web/20170118081253/https://www.sandisk.com/about/media-center/press-releases/2016/western-digital-demonstrates-prototype-of-the-worlds-first-1terabyte-SDXC-card|url-status=live}}</ref>

In August 2017, SanDisk launched a 400&nbsp;GB microSDXC card.<ref>{{cite web|url=http://www.anandtech.com/show/11793/western-digital-launches-sandisk-ultra-microsd-card-with-400-gb-capacity|title=Western Digital Launches SanDisk Ultra microSD Card with 400 GB Capacity|first=Anton|last=Shilov|access-date=2024-09-11|archive-date=2017-08-31|archive-url=https://web.archive.org/web/20170831223632/http://www.anandtech.com/show/11793/western-digital-launches-sandisk-ultra-microsd-card-with-400-gb-capacity|url-status=live}}</ref>

In January 2018, Integral Memory unveiled its 512&nbsp;GB microSDXC card.<ref>{{Cite web|url=https://www.theverge.com/circuitbreaker/2018/1/22/16921108/integral-memory-512gb-microsd-card-largest-ever-memory-storage|title=Integral Memory's new 512GB microSD card is the biggest microSD card yet|last=Integral Memory|website=theverge.com|date=22 January 2018|access-date=2018-06-10|archive-date=2018-06-12|archive-url=https://web.archive.org/web/20180612141951/https://www.theverge.com/circuitbreaker/2018/1/22/16921108/integral-memory-512gb-microsd-card-largest-ever-memory-storage|url-status=live}}</ref> In May 2018, [[PNY Technologies|PNY]] launched a 512&nbsp;GB microSDXC card. In June 2018 [[Kingston Technology|Kingston]] announced its Canvas series of microSD cards which were capable of capacities up to 512&nbsp;GB,{{efn|name="GiB"|reference=here, 1&nbsp;GB = 1 [[Byte#Units based on powers of 2|GiB]] = 2<sup>30</sup> B}}<!--GiB--> in three variations, Select, Go! and React.<ref>{{Cite web|url=https://www.kingston.com/en/company/press/article/50267?ArticleTitle=Kingston%20Digital%20Announces%20New%20%E2%80%98Canvas%E2%80%99%20Series%20of%20Flash%20Cards%20-%20(12%20March)|title=Kingston Digital Announces New 'Canvas' Series of Flash Cards|publisher=Kingston Technology Europe Co LLP|last=Kingston|access-date=2018-11-19|archive-date=2018-11-21|archive-url=https://web.archive.org/web/20181121120000/https://www.kingston.com/en/company/press/article/50267?ArticleTitle=Kingston%20Digital%20Announces%20New%20%E2%80%98Canvas%E2%80%99%20Series%20of%20Flash%20Cards%20-%20(12%20March)|url-status=live}}</ref>

In February 2019, [[Micron Technology|Micron]] and [[SanDisk]] unveiled their microSDXC cards of 1&nbsp;TB capacity.<ref>{{Cite web|url=https://www.theverge.com/2019/5/15/18626729/sandisks-1tb-microsd-card-available-b-h-photo-amazon-price|title=SanDisk's 1TB microSD card is now available|website=theverge.com|date=15 May 2019|access-date=19 December 2019|archive-date=17 June 2020|archive-url=https://web.archive.org/web/20200617090004/https://www.theverge.com/2019/5/15/18626729/sandisks-1tb-microsd-card-available-b-h-photo-amazon-price|url-status=live}}</ref>

In September 2022, [[Kioxia]] unveiled a microSDXC card of 2&nbsp;TB capacity.<ref>{{Cite news |title=Представлена первая в мире карта памяти MicroSDXC ёмкостью 2 ТБ |url=https://www.ixbt.com/news/2022/09/29/predstavlena-pervaja-v-mira-karta-pamjati-microsdxc-jomkostju-2-tb.html |archive-url=https://web.archive.org/web/20250112031849/https://www.ixbt.com/news/2022/09/29/predstavlena-pervaja-v-mira-karta-pamjati-microsdxc-jomkostju-2-tb.html |archive-date=12 January 2025 |access-date=2025-04-03 |date=2022-09-29 |website=iXBT.com |language=ru-RU |url-status=live }}</ref>

=== 2019–present: SDUC ===
The Secure Digital Ultra Capacity (SDUC) format supports cards up to 128&nbsp;TB{{efn|name="here, 1&nbsp;TB = 1024"}} and offers speeds up to 985&nbsp;MB/s.

In April 2024, [[Western Digital]] (SanDisk) revealed the world's first 4&nbsp;TB SD card at [[NAB Show|NAB 2024]], which will make use of the SDUC format. It is set to release in 2025.<ref>{{Cite web |date=11 April 2024 |title=Western Digital Showcases New Super Speeds and Massive Capacities for M&E Workflows at NAB 2024 |url=https://www.westerndigital.com/company/newsroom/press-releases/2024/2024-04-11-western-digital-showcases-new-super-speeds-and-massive-capacities-at-nab-2024 |access-date= |website=westerndigital.com |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911012946/https://www.westerndigital.com/company/newsroom/press-releases/2024/2024-04-11-western-digital-showcases-new-super-speeds-and-massive-capacities-at-nab-2024 |url-status=live}}</ref>

== Capacity ratings ==
Secure Digital includes five card families available in [[#Physical size|three form factors]]. The five families are the original standard capacity (SDSC), high capacity (SDHC), extended capacity ([[#SDXC|SDXC]]), ultra capacity ([[#SDUC|SDUC]]) and [[#SDIO_cards|SDIO]], which combines [[input/output]] functions with data storage.<ref name="sdcard_capacity">{{cite web|title=Capacity|publisher=SD Association|url=http://www.sdcard.org/developers/overview/capacity/|access-date=2011-12-08|archive-date=2020-05-20|archive-url=https://web.archive.org/web/20200520193351/https://www.sdcard.org/developers/overview/capacity/|url-status=live}}</ref><ref name="sdcard_using_sdxc">{{cite web|title=Using SDXC|publisher=SD Association|url=http://www.sdcard.org/consumers/sdxc_capabilities/using_sdxc/|access-date=2011-12-08|archive-date=2014-10-10|archive-url=https://web.archive.org/web/20141010090939/https://www.sdcard.org/consumers/sdxc_capabilities/using_sdxc|url-status=dead}}</ref><ref name="sdcard_sdio">{{cite web|title=SDIO|publisher=SD Association|url=http://www.sdcard.org/developers/overview/sdio/|access-date=2011-12-08|archive-date=2020-05-20|archive-url=https://web.archive.org/web/20200520193351/https://www.sdcard.org/developers/overview/sdio/|url-status=live}}</ref>

{| class="wikitable" style="text-align: center;"
|+ Comparison of capacity standards<ref>{{Cite web |date=2020-12-11 |title=Capacity (SD/SDHC/SDXC/SDUC) {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US |archive-date=8 March 2022 |archive-url=https://web.archive.org/web/20220308120216/https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |url-status=live }}</ref>
!
! scope="col" | SD
! scope="col" | SDHC
! scope="col" | SDXC
! scope="col" | SDUC
|- style="background: white;"
!Mark
| [[File:SD-Logo.svg|frameless|upright=0.25]]
| [[File:SDHC-Logo.svg|frameless|upright=0.25]]
| [[File:SDXC.svg|frameless|upright=0.25]]
| [[File:SDUC.svg|frameless|upright=0.25]]
|-
!Max capacity
| {{Nowrap|2 GB}}
| {{Nowrap|32 GB}}
| {{Nowrap|2 TB}}
| {{Nowrap|128 TB}}
|-
! scope="row" id="Filesys" | File system
| [[FAT12]], [[FAT16]]
| [[FAT32]]
| colspan="2" | [[exFAT]]
|}

=== SD (SDSC) ===
{{More citations needed|section|date=September 2023}}

The original Secure Digital card, also known as Secure Digital Standard Capacity (SDSC), was developed as a second-generation successor to the [[MultiMediaCard]] (MMC) standard. While both formats continued to evolve, they diverged significantly in design and functionality. Secure Digital introduced several key changes to improve usability, durability, and performance:
* Asymmetrical shape of the sides of the SD card prevents inserting it upside down (whereas an MMC goes in most of the way but makes no contact if inverted).{{citation needed|date=September 2023}}
* Most standard size SD cards are {{Convert|2.1|mm|abbr=in}}<ref name="CS">{{Cite web |date=2020-12-11 |title=Capacity (SD/SDHC/SDXC/SDUC) {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |access-date=2023-05-03 |website=sdcard.org |language=en-US |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911012954/https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |url-status=live}}</ref> thick, with microSD versions being {{Convert|1.0|mm|abbr=in}}<ref name="CS" /> thick, compared to {{Convert|1.4|mm|abbr=in}} for MMCs. The SD specification defines a card called '''Thin SD''' with a thickness of 1.4&nbsp;mm,<ref name=":0">{{Cite book |url=https://www.sdcard.org/downloads/pls/pdf/?p=Part1_Physical_Layer_Simplified_Specification_Ver9.10.jpg&f=Part1PhysicalLayerSimplifiedSpecificationVer9.10Fin_20231201.pdf&e=EN_SS9_1 |title=SD Specifications Part 1 Physical Layer Simplified Specification |date=December 1, 2023 |publisher=SD Card Association |edition=9.10 |page=5}}</ref> however it was rarely used, as the SDA went on to define even smaller form factors.
* The card's electrical contacts are recessed beneath the surface of the card, protecting them from contact with a user's fingers.
* The SD specification envisioned capacities and transfer rates exceeding those of MMC, and both of these functionalities have grown over time.{{citation needed|date=September 2023}} For a comparison table, see [[#Comparison to other flash memory formats|below]].
* While MMC uses a single pin for data transfers, the SD card added a four-wire bus mode for higher data rates.{{citation needed|date=September 2023}}
* The SD card added [[Content Protection for Recordable Media]] (CPRM) security circuitry for [[digital rights management]] (DRM) content-protection, although it is rarely used and most devices don't support it.<ref>{{Cite web |title=Definition of CPRM |url=https://www.pcmag.com/encyclopedia/term/cprm |access-date=2025-04-29 |website=PCMAG |language=en |archive-date=29 April 2025 |archive-url=https://web.archive.org/web/20250429025631/https://www.pcmag.com/encyclopedia/term/cprm |url-status=live }}</ref><ref>{{Cite web |title=Copyright Protection for Digital Data (CPRM) |url=https://www.sdcard.org/consumers/about-sd-memory-card-choices/copyright-protection-for-digital-data-cprm/ |access-date=2025-04-29 |website=SD Association |language=en-US |archive-date=29 April 2025 |archive-url=https://web.archive.org/web/20250429025631/https://www.sdcard.org/consumers/about-sd-memory-card-choices/copyright-protection-for-digital-data-cprm/ |url-status=live }}</ref>
* Addition of a write-protect notch{{citation needed|date=September 2023}}

The official SDSC specification supports card sizes up to 2 GB and uses a logo to distinguish it from later SD formats.

Due to physical differences, full-size SD cards are incompatible with slimmer MMC slots, and other electrical and protocol-level differences further limit interoperability between the two formats.{{citation needed|date=September 2023}}

===SDHC===
The Secure Digital High Capacity (SDHC) format, announced in January 2006 and defined in version 2.0 of the SD specification, supports cards with capacities up to 32&nbsp;GB.{{efn|name="GiB"}}<ref name="sdcard_capacity"/> The SDHC trademark is licensed to ensure compatibility.<ref name=sandisk-sdhc>[http://www.sandisk.com/Assets/File/pdf/retail/SDHC1.pdf What are SDHC, miniSDHC, and microSDHC?] SanDisk. {{webarchive |url=https://web.archive.org/web/20080916035153/http://www.sandisk.com/Assets/File/pdf/retail/SDHC1.pdf |date=September 16, 2008}}</ref>

SDHC cards are physically and electrically identical to standard-capacity SD cards (SDSC). The major compatibility issues between SDHC and SDSC cards are the redefinition of the Card-Specific Data (CSD) register in version 2.0 (see [[#Storage capacity calculations|below]]), and the fact that SDHC cards are shipped preformatted with the [[FAT32]] file system.

Version 2.0 also introduces a high-speed bus mode for both SDSC and SDHC cards, which doubles the original Standard Speed clock to produce 25&nbsp;[[MB/s]].<ref name=sd-association>[https://www.sdcard.org/developers/overview/bus_speed/ Bus Speed (Default Speed/ High Speed/ UHS)] {{Webarchive|url=https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |date=2016-10-04}} SDcard.</ref>

SDHC host devices are required to accept older SD cards.<ref name="sdcard.org">[https://www.sdcard.org/consumers/compatibility/ About Compatibility with Host Devices] {{webarchive|url=https://web.archive.org/web/20111121065335/https://www.sdcard.org/consumers/compatibility/ |date=2011-11-21}} SD Association.</ref> However, older host devices do not recognize SDHC or SDXC memory cards, although some devices can do so through a firmware upgrade.<ref>[http://www.jetaudio.com/download/cowon_rn_d2.html#241 What's new in Firmware 2.41 Beta (for COWON D2)] {{Webarchive|url=https://web.archive.org/web/20110828092629/http://www.jetaudio.com/download/cowon_rn_d2.html#241 |date=2011-08-28}} JetAudio.</ref>{{Better source needed|date=June 2021}} Older Windows operating systems released before Windows 7 require patches or service packs to support access to SDHC cards.<ref>{{cite web |url= http://support.microsoft.com/kb/934428 |work= Support |title= 934428 – Hotfix for Windows XP that adds support for SDHC cards that have a capacity of more than 4&nbsp;GB |publisher=Microsoft |date=2008-02-15 |access-date= 2010-08-22 |archive-date= 2010-01-03 |archive-url= https://web.archive.org/web/20100103175653/http://support.microsoft.com/kb/934428 |url-status=live}}</ref><ref>{{cite web |url=http://support.microsoft.com/kb/939772 | work=Support |title=939772 – Some Secure Digital (SD) cards may not be recognized in Windows Vista |publisher=Microsoft |date=2008-05-15 |access-date=2010-08-22 |archive-date=2010-02-09 |archive-url=https://web.archive.org/web/20100209062534/http://support.microsoft.com/kb/939772 |url-status=live}}</ref><ref>{{cite web |url=http://support.microsoft.com/kb/949126 |work=Support |title=949126 – A Secure Digital High Capacity (SDHC) card is not recognized on a Windows Vista Service Pack 1-based computer |publisher=Microsoft |date=2008-02-21 |access-date= 2010-08-22 |archive-date=2010-01-09 |archive-url=https://web.archive.org/web/20100109134743/http://support.microsoft.com/kb/949126 |url-status=live}}</ref>

===SDXC===
The Secure Digital eXtended Capacity (SDXC) format, announced in January 2009 and defined in version 3.01 of the SD specification, supports cards up to 2&nbsp;TB,{{efn|name="here, 1&nbsp;TB = 1024"}} compared to a limit of 32&nbsp;GB{{efn|name="GiB"}} for SDHC cards in the SD 2.0 specification. SDXC adopts Microsoft's [[exFAT]] file system as a mandatory feature.<ref>{{Cite web |url=https://www.sdcard.org/developers/overview/capacity/ |title=Capacity (SD/SDHC/SDXC) |website=SD Association |language=en |access-date=2017-03-20 |archive-date=2011-11-21 |archive-url=https://web.archive.org/web/20111121064806/https://www.sdcard.org/developers/overview/capacity/ |url-status=live}}</ref>

Version 3.01 also introduced the Ultra High Speed (UHS) bus for both SDHC and SDXC cards, with interface speeds from 50&nbsp;MB/s to 104&nbsp;MB/s for four-bit UHS-I bus.<ref name="BS">{{cite web |title=Bus Speed (Default Speed/ High Speed/ UHS) |url=https://www.sdcard.org/developers/overview/bus_speed/ |website=SD Association |access-date=20 March 2017 |language=en |archive-date=4 October 2016 |archive-url=https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |url-status=live}}</ref> (this number has since been exceeded with SanDisk proprietary technology for 170&nbsp;MB/s read, which is not proprietary anymore, as Lexar has the 1066x running at 160&nbsp;MB/s read and 120&nbsp;MB/s write via UHS&nbsp;1, and Kingston also has their Canvas Go! Plus, also running at 170&nbsp;MB/s).<ref>{{Cite web |title=Lexar Professional 1066x microSDXC UHS-I Card SILVER Series |url=https://www.lexar.com/portfolio_page/professional-1066x-microsdhcmicrosdxc-uhs-i-cards-silver-series/ |access-date=2021-04-10 |website=Lexar |language=en |archive-url=https://web.archive.org/web/20210410090638/https://www.lexar.com/portfolio_page/professional-1066x-microsdhcmicrosdxc-uhs-i-cards-silver-series/ |archive-date=2021-04-10}}</ref><ref>{{Cite web |title=SanDisk Extreme PRO SDHC And SDXC UHS-I Card |url=https://shop.westerndigital.com/products/memory-cards/sandisk-extreme-pro-uhs-i-sd#SDSDXXY-064G-GN4IN |access-date=2021-04-10 |website=shop.westerndigital.com |archive-date=2021-04-10 |archive-url=https://web.archive.org/web/20210410090637/https://shop.westerndigital.com/products/memory-cards/sandisk-extreme-pro-uhs-i-sd#SDSDXXY-064G-GN4IN |url-status=live}}</ref><ref>{{Cite web |title=Canvas Go! Plus Class 10 SD Cards – UHS-I, U3, V30 – 64&nbsp;GB–512&nbsp;GB |url=https://www.kingston.com/en/memory-cards/canvas-go-plus-sd-card |access-date=2021-04-10 |website=Kingston Technology Company |language=en-US |archive-date=2021-10-11 |archive-url=https://web.archive.org/web/20211011111151/https://www.kingston.com/en/memory-cards/canvas-go-plus-sd-card |url-status=live}}</ref><ref>{{Cite web |title=Canvas Go! Plus Class 10 microSD Cards – V30, A2 – 64&nbsp;GB–512&nbsp;GB |url=https://www.kingston.com/en/memory-cards/canvas-go-plus-microsd-card |access-date=2021-04-10 |website=Kingston Technology Company |language=en-US}}</ref>

Version 4.0, introduced in June 2011, allows speeds of 156&nbsp;MB/s to 312&nbsp;MB/s over the four-lane (two differential lanes) UHS-II bus, which requires an additional row of physical pins.<ref name="BS"/>

Version 5.0 was announced in February 2016 at CP+ 2016, and added "Video Speed Class" ratings for UHS cards to handle higher resolution video formats like [[8K resolution|8K]].<ref name="sda_video_speed">{{cite web | url = https://www.sdcard.org/press/New_SD_Association_Speed_Class_Supports_8K_and_Multi_File_Video_Recording.pdf |date=2016-02-26 |title=NEW SD ASSOCIATION VIDEO SPEED CLASS SUPPORTS 8K AND MULTI-FILE VIDEO RECORDING | publisher = SD Association | access-date = 2016-03-03 | archive-date = 2016-03-07 |archive-url=https://web.archive.org/web/20160307192442/https://www.sdcard.org/press/New_SD_Association_Speed_Class_Supports_8K_and_Multi_File_Video_Recording.pdf |url-status=dead}}</ref><ref>{{cite web |url=http://www.anandtech.com/show/10105/sd-association-announces-50-specification |title=SD Association Announces SD 5.0 Specification: SD Cards For UHD and 360° Video Capture |date=2016-03-01 |first=Anton |last=Shilov |publisher=Anand Tech |access-date=2016-03-03 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303190529/http://www.anandtech.com/show/10105/sd-association-announces-50-specification |url-status=live}}</ref> The new ratings define a minimal write speed of 90&nbsp;MB/s.<ref name="sd50_video_speed">{{cite web |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Video_Speed_Class-The_new_capture_protocol_of_SD_5.0.pdf |title=Video Speed Class: The new capture protocol of SD 5.0 |publisher=SD Association |date=February 2016 |access-date=2016-03-03 |archive-date=2016-12-23 |archive-url=https://web.archive.org/web/20161223213758/https://www.sdcard.org/downloads/pls/latest_whitepapers/Video_Speed_Class-The_new_capture_protocol_of_SD_5.0.pdf |url-status=dead}}</ref><ref>{{cite web |url=https://www.cinema5d.com/new-video-speed-class-for-sd-cards/ |title=New Video Speed Class for SD Cards |first=Fabian |last=Chaundy |date=2016-02-26 |work=cinema5D |access-date=2016-03-03 |archive-date=2016-03-07 |archive-url=https://web.archive.org/web/20160307015103/https://www.cinema5d.com/new-video-speed-class-for-sd-cards/ |url-status=live}}</ref>

SDXC cards are required to be formatted using [[exFAT]],<ref name="CS" /> but many operating systems will support others.{{citation needed|date=October 2024}}

[[Windows Vista]] (SP1) and later<ref>{{cite web |title=Notable Changes in Windows Vista Service Pack 1 |url=https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/cc709618(v=ws.10) |department=[[Microsoft TechNet|TechNet]] |website=[[Microsoft Docs]] |date=25 July 2008 |access-date=2021-11-07 |archive-date=2021-11-07 |archive-url=https://web.archive.org/web/20211107193722/https://docs.microsoft.com/en-us/previous-versions/windows/it-pro/windows-vista/cc709618(v=ws.10) |url-status=live }}</ref> and [[OS X]] (10.6.5 and later) have native support for exFAT.<ref>{{cite web |url=http://support.apple.com/kb/HT3553 |title=About the SD and SDXC card slots |publisher=Apple Inc. |date=2011-05-03 |access-date=2011-09-05 |archive-date=2011-09-03 |archive-url=https://web.archive.org/web/20110903100124/http://support.apple.com/kb/HT3553 |url-status=live }}</ref><ref>{{cite web |url=http://www.tuxera.com/mac/apple-released-exfat-support-in-os-x-10-6-5-update/ |title=Apple released exFAT support in OS X 10.6.5 update |publisher=Tuxera.com |date=2010-11-22 |access-date=2012-01-04 |archive-date=2012-05-13 |archive-url=https://web.archive.org/web/20120513202527/http://www.tuxera.com/mac/apple-released-exfat-support-in-os-x-10-6-5-update/ |url-status=dead }}</ref> (Windows XP and Server 2003 can support exFAT via an optional update from Microsoft.)<ref>{{cite web|url=https://support.microsoft.com/en-us/kb/955704|title=Description of the exFAT file system driver update package|publisher=Microsoft|date=2011-10-08|access-date=2015-11-27|archive-url=https://web.archive.org/web/20150511025138if_/https://support.microsoft.com/en-us/kb/955704|archive-date=2015-05-11}}</ref>

Most [[Berkeley Software Distribution|BSD]] and [[Linux]] distributions did not have exFAT support for legal reasons, though in Linux kernel 5.4 Microsoft open-sourced the spec and allowed the inclusion of an exFAT driver.<ref>{{cite web |url=https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.4-exFAT-Is-Coming |title=The Initial exFAT Driver Queued For Introduction With The Linux 5.4 Kernel |publisher=phoronix.com |date=2019-08-30 |access-date=2020-02-05 |archive-date=2019-12-18 |archive-url=https://web.archive.org/web/20191218061425/https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.4-exFAT-Is-Coming |url-status=live }}</ref> Users of older kernels or BSD can manually install third-party implementations of exFAT (as a [[Filesystem in Userspace|FUSE]] module) in order to be able to mount exFAT-formatted volumes.<ref>{{cite web |url=https://code.google.com/p/exfat/ |title=exFAT for BSD and Linux systems from Google Code |access-date=2014-01-02 |archive-date=2014-01-11 |archive-url=https://web.archive.org/web/20140111120127/http://code.google.com/p/exfat/ |url-status=live }}</ref> However, SDXC cards can be reformatted to use any file system (such as [[ext4]], [[Unix File System|UFS]], [[VFAT]] or [[NTFS]]), alleviating the restrictions associated with exFAT availability.

The SD Association provides a formatting utility for Windows and Mac OS X that checks and formats SD, SDHC, SDXC and SDUC cards.<ref>{{cite web |url=https://www.sdcard.org/downloads/formatter_4/ |title=SD Formatter 4.0 for SD/SDHC/SDXC – SD Association |publisher=Sdcard.org |access-date=2014-01-02 |archive-date=2014-02-07 |archive-url=https://web.archive.org/web/20140207233443/https://www.sdcard.org/downloads/formatter_4/ |url-status=live }}</ref>

Except for the change of file system, SDXC cards are mostly backward compatible with SDHC readers, and many SDHC host devices can use SDXC cards if they are first reformatted to the FAT32 file system.<ref>{{cite web |title=Updated: How to upgrade your 3DS SD card, to 64GB and beyond |author=deKay |date=15 January 2015 |website=Lofi-Gaming |url=https://lofi-gaming.org.uk/blog/2013/10/25/updated-how-to-upgrade-your-3ds-sd-card-to-64gb-and-beyond/ |access-date=2018-12-21 |archive-date=2018-12-21 |archive-url=https://web.archive.org/web/20181221134714/https://lofi-gaming.org.uk/blog/2013/10/25/updated-how-to-upgrade-your-3ds-sd-card-to-64gb-and-beyond/ |url-status=live }}</ref><ref>{{cite web |title=Ask Hackaday: How On Earth Can A 2004 MP3 Player Read An SDXC Card? |first=Jenny |last=List |date=29 November 2017 |website=Hackaday |url=https://hackaday.com/2017/11/29/ask-hackaday-how-on-earth-can-a-2004-mp3-player-read-an-sdxc-card/ |access-date=2018-12-21 |archive-date=2018-12-21 |archive-url=https://web.archive.org/web/20181221182601/https://hackaday.com/2017/11/29/ask-hackaday-how-on-earth-can-a-2004-mp3-player-read-an-sdxc-card/ |url-status=live }}</ref><ref>{{cite web |title=High capacity microSD cards and Android – Gary explains |first=Gary |last=Sims |date=9 May 2016 |website=Android Authority |url=https://www.androidauthority.com/high-capacity-microsd-cards-android-gary-explains-690710/ |access-date=2018-12-21 |archive-date=2018-11-22 |archive-url=https://web.archive.org/web/20181122092400/https://www.androidauthority.com/high-capacity-microsd-cards-android-gary-explains-690710/ |url-status=live }}</ref>

===SDUC===
The Secure Digital Ultra Capacity (SDUC) format, described in the SD 7.0 specification, and announced in June 2018, supports cards up to 128&nbsp;TB,{{efn|name="here, 1&nbsp;TB = 1024"}} regardless of form factor, either micro or full size, or interface type including UHS-I, UHS-II, UHS-III or SD Express.<ref>{{cite web |title=SD Express Cards with PCIe and NVMeTM Interfaces |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf |publisher=SD Association |access-date=21 November 2018 |date=June 2018 |archive-url=https://web.archive.org/web/20201112011753/https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf |archive-date=2020-11-12}}</ref>

== Bus speed ratings ==

SD card performance is commonly measured by its sequential read and write speeds. These metrics are especially relevant for applications involving large files, such as photos and videos, where data is accessed in contiguous blocks. In contrast, performance for smaller files—such as directory metadata or configuration files—depends more on random access speed, often measured in input/output operations per second (IOPS). Random access performance can vary significantly between cards and may be a limiting factor in some use cases.<ref name="necstudy">{{cite conference |last1=Kim |first1=H. |last2=Agrawal |first2=N. |last3=Ungureanu |first3=C. |title=Revisiting Storage for Smartphones |conference=USENIX Conference on File and Storage Technologies (FAST) |publisher=NEC Laboratories America |date=2012-01-30 |url=http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf |archive-url=https://web.archive.org/web/20121010194100/http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf |archive-date=2012-10-10 |access-date=2012-12-27 |quote=Speed class considered irrelevant: our benchmarking reveals that the "speed class" marking on SD cards is not necessarily indicative of application performance; although the class rating is meant for sequential performance, we find several cases in which higher-grade SD cards performed worse than lower-grade ones overall.}}</ref><ref name="Gough2014">{{cite web |last=Lui |first=Gough |title=SD Card Sequential, Medium & Small Block Performance Round-Up |url=http://goughlui.com/2014/01/16/testing-sd-card-performance-round-up/ |website=Gough's techzone |date=2014-01-16 |access-date=2015-11-29 |archive-url=https://web.archive.org/web/20151208112031/http://goughlui.com/2014/01/16/testing-sd-card-performance-round-up/ |archive-date=2015-12-08 |quote=Variations in 4k small block performance saw a difference of approximately 300-fold between the fastest and slowest cards. Distressingly, many of the tested cards were mediocre to poor on that metric, which may explain why running updates on Linux running off SD cards can take a very long time.}}</ref><ref>{{cite web |title=Raspberry Pi forum: SD card benchmarks |url=http://www.raspberrypi.org/forums/viewtopic.php?t=4076 |access-date=2014-08-12 |archive-url=https://web.archive.org/web/20140813011920/http://www.raspberrypi.org/forums/viewtopic.php?t=4076 |archive-date=2014-08-13 |url-status=live}}</ref>

Subsequent generations of SD cards have improved performance primarily by increasing the bus speed—the frequency of the clock signal used to transfer data between the card and the host device. Regardless of the bus rate, the card can signal that it is "busy" while completing a read or write operation. Compliance with higher speed ratings generally means that the card reduces its reliance on the "busy" signal, allowing for more efficient data transfers.

{| class="wikitable" style="text-align: center;"
|+ Comparison of bus speeds<ref>{{Cite web |date=2020-12-11 |title=Bus Speed (Default Speed/High Speed/UHS/SD Express) {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/bus-speed-default-speed-high-speed-uhs-sd-express/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US}}</ref>
! rowspan="2" scope="colgroup" |
!  rowspan="2" |Mark
! colspan="3" |Bus
! colspan="4" scope="colgroup" | Standards
! rowspan="2" scope="col" | {{Abbr|Spec|Specification}}
|-
! scope="col" | Speed
! scope="col" | [[PCI Express|PCIe]]
! scope="col" | [[Duplex (telecommunications)|Duplex]]
! scope="col" | SD
! scope="col" | SDHC
! scope="col" | SDXC
! scope="col" | SDUC
|-
! scope="row" | Default
| {{N/a}}
| {{Nowrap|12.5 MB/s}}
| rowspan="8" {{N/a}}
| Half
| rowspan="2" {{Yes}}
| rowspan="11" {{Yes}}
| rowspan="11" {{Yes}}
| rowspan="11" {{Yes}}
| 1.01
|-
! scope="row" | {{Nowrap|High Speed}}
| {{N/a}}
| {{Nowrap|25 MB/s}}
|Half
| 1.10
|-
! scope="row" rowspan="2" | UHS-I
| rowspan="2" style="background:white" | [[File:UHS-I.svg|x20px]]
| {{Nowrap|50 MB/s}}
| rowspan="2" |Half
| rowspan="9" {{No}}
| rowspan="2" | 3.01
|-
| {{Nowrap|104 MB/s}}
|-
! scope="row" rowspan="2" | UHS-II
| rowspan="2" style="background:white" | [[File:UHS-II.svg|x20px]]
| {{Nowrap|156 MB/s}}
| Full
| rowspan="2" | 4.00
|-
| {{Nowrap|312 MB/s}}
| Half
|-
! scope="row" rowspan="2" | UHS-III
| rowspan="2" style="background:white" | [[File:UHS-III.svg|x20px]]
| {{Nowrap|312 MB/s}}
| rowspan="2" | Full
| rowspan="2" | 6.00
|-
| {{Nowrap|624 MB/s}}
|-
! scope="row" rowspan="3" | SD Express
| rowspan="3" style="background:white" | [[File:SDex(short).svg|x20px]]
| {{Nowrap|985 MB/s}}
| {{Nowrap|3.1 ×1}}
| rowspan="3" {{N/a}}
| 7.00, 7.10
|-
| {{Nowrap|1,970 MB/s}}
| {{Nowrap|3.1 ×2}}, {{Nowrap|4.0 ×1}}
| rowspan="2"| 8.0
|-
| {{Nowrap|3,940 MB/s}}
| {{Nowrap|4.0 ×2}}
|}

{| class="wikitable collapsible collapsed" style="text-align: center;"
|+Bus speed of host and card combinations (in MB/s)<ref>{{Cite journal|date=June 2018|title=SD Express Cards with Pie and Name Interfaces|url=https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf|journal=SD Association|pages=9|access-date=2018-06-27|archive-date=2020-11-12|archive-url=https://web.archive.org/web/20201112011753/https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf|url-status=dead}}</ref>
! colspan="2" rowspan="2" {{Diagonal split header 2|Card|Host}}
! colspan="2" | UHS-I
! colspan="2" | UHS-II
! rowspan="2" | UHS-III
! rowspan="2" | Express
|-
! UHS50
! UHS104
! {{Abbr|Full|Full-duplex}}
! {{Abbr|Half|Half-duplex}}
|-
! rowspan="2" |UHS-I
! UHS50
|'''{{0|0}}50'''
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|-
! UHS104
|{{0|0}}50
|'''104'''
|104
|104
|104
|104
|-
! rowspan="2" |UHS-II
! {{Abbr|Full|Full-duplex}}
|{{0|0}}50
|104
|'''156'''
|156
|156
|104
|-
! {{Abbr|Half|Half-duplex}}
|{{0|0}}50
|104
|156
|'''312'''
|312
|104
|-
! colspan="2" |UHS-III
|{{0|0}}50
|104
|156
|312
|'''624'''
|104
|-
! colspan="2" |Express
|{{0|0}}50
|104
|104
|104
|104
|'''985'''
|}

=== Default Speed ===
The original SD bus interface, introduced with version 1.00 of the SD specification, supported a maximum transfer rate of 12.5&nbsp;MB/s. This mode is referred to as '''Default Speed'''.

=== High Speed ===
With version 1.10 of the specification, the SD Association introduced '''High-Speed''' mode, which increased the maximum transfer rate to 25&nbsp;MB/s. This enhancement was designed to meet the growing performance requirements of devices such as digital cameras.<ref>{{cite web |url=https://www.sdcard.org/developers/overview/bus_speed/ |title=Bus Speed (Default Speed/High Speed/UHS/SD Express) |publisher=SD Association |access-date=2020-04-18 |archive-url=https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |archive-date=2016-10-04 |url-status=live }}</ref>

=== {{Anchor|Ultra High Speed|UHS}} UHS (Ultra High Speed) ===

The '''Ultra High Speed''' ('''UHS''') bus is a type of interface used by some [[Secure Digital#SDHC|SDHC]] and [[Secure Digital#SDXC|SDXC]] cards to enable faster data transfer between the card and a host device.<ref name="sda_bus_speed">{{cite web |url=https://www.sdcard.org/developers/overview/bus_speed/ |title=Bus Speed (Default Speed/ High Speed/ UHS) |publisher=SD Association |access-date=2013-11-13 |archive-date=2016-10-04 |archive-url=https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |url-status=live }}</ref><ref>{{cite web |url=https://www.engadget.com/2010/06/24/sd-cards-branded-with-an-upper-case-i-are-faster-yo/ |title=SD cards branded with an upper-case 'I' are faster, yo |publisher=Engadget |date=2010-06-24 |access-date=2010-08-22 |archive-date=2010-08-28 |archive-url=https://web.archive.org/web/20100828145021/http://www.engadget.com/2010/06/24/sd-cards-branded-with-an-upper-case-i-are-faster-yo/ |url-status=live }}</ref>

UHS-compatible cards are marked with Roman numerals next to the SD logo, indicating the version of the UHS standard they support.<ref name="sda_bus_speed"/><ref name="sda_speed_class">{{cite web |title=SD Speed Class |url=https://www.sdcard.org/developers/overview/speed_class |url-status=dead |archive-url=https://web.archive.org/web/20201221172542/https://www.sdcard.org/developers/overview/speed_class/ |archive-date=2020-12-21 |access-date=2013-11-13 |publisher=SD Association}}</ref> These cards offer significantly faster read and write speeds than earlier SD card types, making them well suited for high-resolution video, burst photography, and other data-intensive applications.

To achieve higher transfer speeds, UHS cards and devices use specialized electrical signaling and hardware interfaces. UHS-I cards operate at 1.8&nbsp;V instead of the standard 3.3&nbsp;V and use a four-bit transfer mode. UHS-II and UHS-III introduce a second row of interface pins and use [[low-voltage differential signaling]] (LVDS) at 0.4&nbsp;V to increase speed and reduce power consumption and electromagnetic interference (EMI).<ref>{{cite web |title=SD Standard Overview |url=https://www.sdcard.org/developers/sd-standard-overview/ |website=SD Association |date=2020-12-11 |access-date=2023-06-19}}</ref>

Each LVDS lane can transfer up to 156&nbsp;MB/s. In full-duplex mode, one lane is used for sending data and the other for receiving. In half-duplex mode, both lanes operate in the same direction, effectively doubling the data rate at the same clock speed.

The following UHS speed classes are defined:

==== UHS-I ====

Support for the Ultra High Speed interface was first specified in SD version 3.01, released in May 2010.<ref name="SDHCspec">{{cite web |publisher=SD Association |url=http://www.sdcard.org/downloads/pls/simplified_specs/archive/part1_301.pdf |title=SD Part 1, Physical Layer Simplified Specification, Version 3.01 |date=2010-05-18 |access-date=2013-11-25 |archive-url=https://web.archive.org/web/20131205014133/https://www.sdcard.org/downloads/pls/simplified_specs/archive/part1_301.pdf |archive-date=2013-12-05 |url-status=dead }}</ref> This version introduced support for a 100&nbsp;MHz clock frequency—four times the rate of the original "Default Speed"—which enabled transfer rates up to 50&nbsp;MB/s using four-bit Single Data Rate (SDR) transfers, designated as '''SDR50'''. An extended mode called '''SDR104''' (also part of UHS-I) further increased the clock frequency to 208&nbsp;MHz, enabling data rates up to 104&nbsp;MB/s.

Version 3.01 also introduced '''DDR50''', a [[double data rate]] mode that transmits data on both the rising and falling edges of the clock signal. At 50&nbsp;MHz, DDR50 can achieve 50&nbsp;MB/s transfer rates by sending four bits per edge, or eight bits (one byte) per full clock cycle. This mode is mandatory for microSDHC and microSDXC cards labeled as UHS-I.

A proprietary extension of UHS-I, known as '''DDR200''', was developed by SanDisk to further increase transfer speeds without requiring additional pins. It combines double data rate transfers with the 208&nbsp;MHz clock of SDR104 to reach speeds of up to 170&nbsp;MB/s.<ref>{{cite web |title=SanDisk Extreme microSDXC datasheet |url=https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/sandisk/product/memory-cards/extreme-uhs-i-microsd/data-sheet-extreme-uhs-i-microsd.pdf |website=Western Digital |access-date=2021-02-04 |archive-date=2021-01-08 |archive-url=https://web.archive.org/web/20210108210349/https://documents.westerndigital.com/content/dam/doc-library/en_us/assets/public/sandisk/product/memory-cards/extreme-uhs-i-microsd/data-sheet-extreme-uhs-i-microsd.pdf |url-status=live }}</ref><ref>{{cite web |title=GL3232 |url=http://www.genesyslogic.com/en/product_view.php?show=83 |website=Genesys Logic |access-date=2021-02-04 |archive-date=2020-09-21 |archive-url=https://web.archive.org/web/20200921071215/http://www.genesyslogic.com/en/product_view.php?show=83 |url-status=live }}</ref> Although not part of the official SD specification, DDR200 has been adopted by several manufacturers, including Lexar (1066x series, up to 160&nbsp;MB/s), Kingston (Canvas Go Plus, up to 170&nbsp;MB/s), and MyMemory (PRO SD card, up to 180&nbsp;MB/s).

==== UHS-II ====
[[File:Lexar 1000x MicroSDHC UHS-II U3 Class 10 - Back.jpg|thumb|upright|Back side of a Lexar UHS-II microSDHC card, showing the additional row of UHS-II connections]]

Specified in version 4.0, further raises the data transfer rate to a theoretical maximum of 156&nbsp;MB/s (full-[[Duplex (telecommunications)|duplex]]) or 312&nbsp;MB/s (half-duplex) using an additional row of pins for LVDS signalling<ref name="firstsdxc">{{cite web | url = https://www.sdcard.org/press/SD_Association_Announces_UHS-II_eBOOK_Jan_5_2011_ENGLISH.PDF | publisher = SD Card | title = Association Triples Speeds with UHS-II | date = 5 January 2011 | access-date = 2011-08-09 | archive-date = 2011-03-21 | archive-url = https://web.archive.org/web/20110321195143/http://www.sdcard.org/press/SD_Association_Announces_UHS-II_eBOOK_Jan_5_2011_ENGLISH.PDF | url-status = dead }}</ref> (a total of 17 pins for full-size and 16 pins for micro-size cards).<ref name="sda_bus_speed"/> While first implementations in compact system cameras were seen three years after specification (2014), it took many more years until UHS-II was implemented on a regular basis. At the beginning of 2025, 100 DSLR and mirrorless cameras support UHS-II.<ref>{{cite web |url=https://www.memorycard-lab.com/-Article/UHS-II-Cameras | publisher = memorycard-lab.com | title = UHS-II camera list | access-date=2025-01-04}}</ref>

==== UHS-III ====
Version 6.0, released in February 2017, added two new data rates to the standard. FD312 provides 312&nbsp;MB/s while FD624 doubles that. Both are full-duplex. The physical interface and pin-layout are the same as with UHS-II, retaining backward compatibility.<ref>{{Cite web|url=https://www.sdcard.org/press/DoublesTransferSpeeds_with_UHS3_2_9_2017.pdf|title=SD Association Doubles Bus Interface Speeds with UHS-III|date=23 February 2017|access-date=23 February 2017|archive-date=24 February 2017|archive-url=https://web.archive.org/web/20170224211349/https://www.sdcard.org/press/DoublesTransferSpeeds_with_UHS3_2_9_2017.pdf|url-status=dead}}</ref>

=== {{anchor|Express}} SD Express ===
[[File:SD Express Highest Speed Card Standard.jpg|thumb|Front and back of an SD Express card]]

The SD Express bus was introduced in June 2018 with the SD 7.0 specification. By incorporating a single [[PCI Express 3.0]] (PCIe) lane and supporting the [[NVM Express]] (NVMe) storage protocol, SD Express enables full-duplex transfer speeds of up to 985&nbsp;MB/s. Compatible cards must support both PCIe and NVMe, and may be formatted as SDHC, SDXC, or SDUC. For backward compatibility, they are also required to support the High-Speed and UHS-I buses. The interface reuses the UHS-II pin layout and reserves space for two additional pins for future use.<ref>{{cite web |date=June 27, 2018 |title=SD Express Card Spec Announced – PCIe + NVMe Up To 985 MB/s |url=https://www.anandtech.com/show/12902/sd-express-card-spec-announced-pcie-nvme-up-to-985mbs |website=AnandTech |access-date=12 April 2025 |archive-date=12 April 2025 |archive-url=https://web.archive.org/web/20250412032606/https://www.anandtech.com/show/12902/sd-express-card-spec-announced-pcie-nvme-up-to-985mbs |url-status=live }}</ref> In February 2019, the SD Association announced microSD Express,<ref>{{cite news |last=Gartenberg |first=Chain |date=25 February 2019 |title=Memory cards are about to get much faster with new microSD Express spec |url=https://www.theverge.com/circuitbreaker/2019/2/25/18239558/microsd-express-sd-association-new-format-speed-faster-mwc-2019-data-transfer |url-status=live |archive-url=https://web.archive.org/web/20190315212414/https://www.theverge.com/circuitbreaker/2019/2/25/18239558/microsd-express-sd-association-new-format-speed-faster-mwc-2019-data-transfer |archive-date=15 March 2019 |access-date=18 March 2019 |work=The Verge}}</ref> along with new visual marks to help users identify compatible cards and hosts.<ref>{{cite news |last=Henchman |first=Mark |date=25 February 2019 |title=The microSD Express standard combines PCI Express speeds, microSD convenience |url=https://www.pcworld.com/article/3343067/the-microsd-express-standard-combines-pci-express-speeds-microsd-convenience.html |url-status=live |archive-url=https://web.archive.org/web/20190808085536/https://www.pcworld.com/article/3343067/the-microsd-express-standard-combines-pci-express-speeds-microsd-convenience.html |archive-date=8 August 2019 |access-date=18 March 2019}}</ref>

SD Express cards can perform [[direct memory access]] (DMA), boosting performance but also increasing the host system’s attack surface in the event of a malicious or compromised card.<ref>{{cite web |date=May 19, 2022 |title=When microSD Cards Turn Against You |url=https://research.nccgroup.com/2022/05/19/when-microsd-cards-turn-against-you/ |website=NCC Group}}</ref>

The SD 8.0 specification, announced on 19 May 2020, expanded the bus interface to support [[PCIe 4.0]] on all cards and dual lanes on full-size cards. With dual lane PCIe 4.0, this update raised theoretical maximum transfer speeds to 3,938&nbsp;MB/s using an additional row of contacts.<ref>{{Cite press release |title=SDExpress Delivers New Gigabtye Speeds For SDMemory Cards |publisher=SD association |url=https://www.sdcard.org/press/whatsnew/SDExpressDeliversNewGigabtyeSpeedsForSDMemoryCards.pdf |access-date=2020-05-19 |url-status=live |archive-url=https://web.archive.org/web/20200520193348/https://www.sdcard.org/press/whatsnew/SDExpressDeliversNewGigabtyeSpeedsForSDMemoryCards.pdf |archive-date=2020-05-20 |work=SD card}}</ref> Revisions continued with version 9.0 in February 2022<ref>{{Cite web |title=sd 9.0 |url=https://www.sdcard.org/cms/wp-content/uploads/2022/05/SD-SPECIFICATION-9-%E2%80%93NEW-OPPORTUNITIES-FOR-SD-MEMORY-CARDS_EN.pdf |url-status=live |archive-url=https://web.archive.org/web/20240802052922/https://www.sdcard.org/cms/wp-content/uploads/2022/05/SD-SPECIFICATION-9-%E2%80%93NEW-OPPORTUNITIES-FOR-SD-MEMORY-CARDS_EN.pdf |archive-date=August 2, 2024 |accessdate=July 31, 2024}}</ref> and version 9.1 in October 2023,<ref name="SDver9.1">{{Cite web |date=2023-10-27 |title=New SD Express Specifications Introduce New Speed Classes and Next-Level Performance Features {{!}} SD Association |url=https://www.sdcard.org/press/thoughtleadership/sd-9-1-specification-introduces-new-speed-classes-and-next-level-performance-features-2/ |url-status=live |archive-url=https://web.archive.org/web/20240401075430/https://www.sdcard.org/press/thoughtleadership/sd-9-1-specification-introduces-new-speed-classes-and-next-level-performance-features-2/ |archive-date=2024-04-01 |access-date=2024-04-01 |website=www.sdcard.org |language=en-US}}</ref> further refining the standard.

Adoption has been gradual. In February 2024, [[Samsung]] announced it was sampling its first microSD Express cards,<ref>{{Cite web |last=Cunningham |first=Andrew |date=2024-02-28 |title=Speedy "SD Express" cards have gone nowhere for years, but Samsung could change that |url=https://arstechnica.com/gadgets/2024/02/sd-express-cards-from-samsung-promise-faster-than-sata-speeds-for-microsd-devices/ |access-date=2025-04-09 |website=Ars Technica |language=en-US |archive-date=9 April 2025 |archive-url=https://web.archive.org/web/20250409140340/https://arstechnica.com/gadgets/2024/02/sd-express-cards-from-samsung-promise-faster-than-sata-speeds-for-microsd-devices/ |url-status=live }}</ref> though commercial availability remained limited. Interest increased when Nintendo confirmed in April 2025 that the upcoming [[Nintendo Switch 2|Switch 2]] would only support microSD Express cards, without backwards compatibility for UHS-I cards.<ref>{{Cite web |last=Anderson |first=Robert |date=2025-04-04 |title=You Can Already Buy Switch 2 Compatible MicroSD Express Cards |url=https://www.ign.com/articles/nintendo-switch-2-microsd-express-cards-where-to-buy |access-date=2025-04-09 |website=IGN |language=en}}</ref>

== Card speed class ratings ==
'''Speed Class ratings''' are defined by the SDA to indicate the minimum data transfer performance of SDHC and SDXC memory cards, particularly in terms of sustained sequential write speed. These ratings are especially important for applications such as video recording, which require consistent throughput.<ref name="sda_speed_class" />

Where speed classes overlap, manufacturers often display multiple symbols on the same card to indicate compatibility with different host devices and standards.
{| class="wikitable" style="text-align: center;"
|+ Comparison of card speed class ratings<ref>{{Cite web |date=2020-12-11 |title=Speed Class {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/speed-class/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US |archive-date=4 January 2025 |archive-url=https://web.archive.org/web/20250104004951/https://www.sdcard.org/developers/sd-standard-overview/speed-class/ |url-status=live }}</ref>
! scope="col" rowspan="2" | {{Abbr|Min speed|Minimum serial data writing speed}}
! scope="colgroup" colspan="4" | Speed Class
! scope="colgroup" colspan="4" | [[Video format]]{{Efn|The necessary recording and playback speed class requirements may vary by device.}}
|-
! scope="col" | Original
! scope="col" | UHS
! scope="col" | Video
! scope="col" | SD Express
! scope="col" | [[Standard-definition television|SD]]
! scope="col" | [[High-definition video|HD]]
! scope="col" | [[4K resolution|4K]]
! scope="col" | [[8K resolution|8K]]
|-
! scope="row" | {{Nowrap|2 MB/s}}
| style="background:white" | {{Nowrap|Class 2 (C2)}}<br/>[[File:SDHC Speed Class 2.svg|x20px]]
| rowspan="3" {{N/a}}
| rowspan="2" {{N/a}}
| rowspan="7" {{N/a}}
| rowspan="11" {{Yes}}
| {{No}}
| rowspan="2" {{No}}
| rowspan="4" {{No}}
|-
! scope="row" | {{Nowrap|4 MB/s}}
| style="background:white" | {{Nowrap|Class 4 (C4)}}<br/>[[File:SDHC Speed Class 4.svg|x20px]]
| rowspan="10" {{Yes}}
|-
! scope="row" | {{Nowrap|6 MB/s}}
| style="background:white" | {{Nowrap|Class 6 (C6)}}<br/>[[File:SDHC Speed Class 6.svg|x20px]]
| style="background:white" | {{Nowrap|Class 6 (V6)}}<br/>[[File:SD Video Speed Class 6.svg|x20px]]
| rowspan="9" {{Yes}}
|-
! scope="row" | {{Nowrap|10 MB/s}}
| style="background:white" | {{Nowrap|Class 10 (C10)}}<br/>[[File:SDHC Speed Class 10.svg|x20px]]
| style="background:white" | {{Nowrap|Class 1 (U1)}}<br/>[[File:SD UHS Speed Class 1.svg|x20px]]
| style="background:white" | {{Nowrap|Class 10 (V10)}}<br/>[[File:SD Video Speed Class 10.svg|x20px]]
|-
! scope="row" | {{Nowrap|30 MB/s}}
| rowspan="7" {{N/a}}
| style="background:white" | {{Nowrap|Class 3 (U3)}}<br/>[[File:SD UHS Speed Class 3.svg|x20px]]
| style="background:white" | {{Nowrap|Class 30 (V30)}}<br/>[[File:SD Video Speed Class 30.svg|x20px]]
| rowspan="7" {{Yes}}
|-
! scope="row" | {{Nowrap|60 MB/s}}
| rowspan="6" {{N/a}}
| style="background:white" | {{Nowrap|Class 60 (V60)}}<br/>[[File:SD Video Speed Class 60.svg|x20px]]
|-
! scope="row" | {{Nowrap|90 MB/s}}
| style="background:white" | {{Nowrap|Class 90 (V90)}}<br/>[[File:SD Video Speed Class 90.svg|x20px]]
|-
! scope="row" | {{Nowrap|150 MB/s}}
| rowspan="4" {{N/a}}
| style="background:white" | {{Nowrap|Class 150 (E150)}}<br/>[[File:SD Express Class 150.svg|41x41px]]
|-
! scope="row" | {{Nowrap|300 MB/s}}
| style="background:white" | {{Nowrap|Class 300 (E300)}}<br/>[[File:SD Express Class 300.svg|41x41px]]
|-
! scope="row" | {{Nowrap|450 MB/s}}
| style="background:white" | {{Nowrap|Class 450 (E450)}}<br/>[[File:SD Express Class 450.svg|41x41px]]
|-
! scope="row" | {{Nowrap|600 MB/s}}
| style="background:white" | {{Nowrap|Class 600 (E600)}}<br/>[[File:SD Express Class 600.svg|41x41px]]
|}

=== Original speed class (C) ===
The original speed class ratings—Class 2, 4, 6, and 10—specify minimum sustained write speeds of 2, 4, 6, and 10&nbsp;MB/s, respectively. Class 10 cards assume a non-fragmented file system and use the High Speed bus mode.<ref name="SDHCspec" /> These are represented by a number encircled with a "C" (e.g., C2, C4, C6 and C10).

=== UHS speed class (U) ===
Ultra High Speed (UHS) speed class ratings—U1 and U3—specify minimum sustained write speeds of 10 and 30&nbsp;MB/s, respectively. These classes are represented by a number inside a "U" and are designed for high-bandwidth tasks such as [[4K video]] recording.<ref>{{cite web |title=NEW SDXC AND SDHC MEMORY CARDS SUPPORT 4K2K VIDEO |url=https://www.sdcard.org/home/New_SDXC_and_SDHC_Memory_Cards_Now_Support_4K2K_Video_11-6-2013_FINAL_2.pdf |url-status=live |archive-url=https://web.archive.org/web/20131113000144/https://www.sdcard.org/home/New_SDXC_and_SDHC_Memory_Cards_Now_Support_4K2K_Video_11-6-2013_FINAL_2.pdf |archive-date=2013-11-13 |access-date=2013-11-13 |publisher=SD Association}}</ref>

=== Video speed class (V) ===
Video speed class ratings—V6, V10, V30, V60, and V90—specify minimum sustained write speeds of 6, 10, 30, 60, and 90&nbsp;MB/s, respectively.<ref name="sda_video_speed" /><ref name="sda_speed_class" /><ref name="sda_speed_class_consumer">{{cite web |date=11 December 2020 |title=Speed Class Standards for Video Recording – SD Association |url=https://www.sdcard.org/consumers/choices/speed_class/index.html |url-status=live |archive-url=https://web.archive.org/web/20160407123207/https://www.sdcard.org/consumers/choices/speed_class/index.html |archive-date=7 April 2016 |access-date=28 April 2016 |website=sdcard.org}}</ref> These classes are represented by a stylized "V" followed by the number, were introduced to support high-resolution formats like 4K and [[Ultra-high-definition television|8K]], and to align with the performance characteristics of [[Multi-level cell|MLC NAND flash]] memory.<ref name="sd50_video_speed" />

=== SD Express Speed Class (E) ===
SD Express speed class ratings—E150, E300, E450, and E600—specify minimum sustained write speeds of 150, 300, 450, and 600&nbsp;MB/s, respectively.<ref name="SDver9.1" /> These classes are represented by a stylized "E" followed by the number, enclosed in a rounded rectangle. They are designed for data-intensive applications such as large-scale video processing, real-time analytics, and software execution.<ref name="SDver9.1" />

=== "×" rating ===
{{main|CD and DVD writing speed}}

{| class="wikitable" style="background:white; float:right; margin-left:1em;"
|-
! valign="top" | Rating
! valign="top" | Approx.<br />(MB/s)
! valign="top" | Comparable<br />speed class
|- style="text-align:center;"
| 16×
| 2.34
| [[File:SDHC Speed Class 2.svg|28px]] (13×)
|- style="text-align:center;"
| 32×
| 4.69
| [[File:SDHC Speed Class 4.svg|28px]] (27×)
|- style="text-align:center;"
| 48×
| 7.03
| [[File:SDHC Speed Class 6.svg|28px]] (40×)
|- style="text-align:center;"
| 100×
| 14.6
| [[File:SD Class 10.svg|28px]] (67×)
|}

Initially, some manufacturers used a "×" rating system based on the speed of a standard [[Optical disc drive|CD-ROM drive]] (150&nbsp;kB/s or 1.23&nbsp;[[Mbit/s]]),{{efn|reference=1 KB = 1024 B}} but this approach was inconsistent and often unclear. It was later replaced by standardized Speed Class systems that specify guaranteed minimum write speeds.<ref name="SDHCspec" /><ref name="sda_speed_class_consumer" /><ref name="sda_logos_2017">{{Cite web |title=SD Standards Brochure 2017 |url=https://www.sdcard.org/consumers/pdf/2017SDA_brochure_eng.pdf |url-status=dead |archive-url=https://web.archive.org/web/20170330174639/https://www.sdcard.org/consumers/pdf/2017SDA_brochure_eng.pdf |archive-date=2017-03-30 |access-date=2017-03-29}}</ref><ref>{{cite web |title=Flash Memory Cards and X-Speed Ratings |url=http://www.kingston.com/us/flash/x-speed |url-status=dead |archive-url=https://web.archive.org/web/20170702204220/http://www.kingston.com/us/flash/x-speed |archive-date=2017-07-02 |access-date=2017-08-05 |publisher=Kingston}}</ref>

=== Real-world performance ===
Speed Class ratings guarantee minimum write performance but do not fully describe real-world speed, which can vary based on factors such as [[file fragmentation]], [[write amplification]] due to flash memory management, controller retry operations for soft error correction and sequential vs. random write patterns.

In some cases, cards of the same speed class may perform very differently. For instance, random small-file write speeds can be significantly lower than sequential performance. A 2012 study found some Class 2 cards outperformed Class 10 cards in random writes.<ref name="necstudy" /> Another test in 2014 reported a 300-fold difference in small-write performance across cards, with a Class 4 card outperforming higher-rated cards in certain use cases.<ref name="Gough2014" />

== Relationship between bus modes and card speed classes ==
Each labeled card speed class requires a minimum bus speed mode in which it can function.  The following table illustrates this relationship in addition to which of the card capacity types are available in each bus mode.<ref>{{Cite book |url=https://www.sdcard.org/downloads/pls/pdf/?p=Part1_Physical_Layer_Simplified_Specification_Ver9.10.jpg&f=Part1PhysicalLayerSimplifiedSpecificationVer9.10Fin_20231201.pdf&e=EN_SS9_1 |title=SD Specifications Part 1 Physical Layer Simplified Specification |date=December 1, 2023 |publisher=SD Card Association |edition=9.10 |page=138}}</ref><ref>{{Cite web |title=Bus Interface Speed Standards for Large Size Data Transfer |url=https://www.sdcard.org/consumers/about-sd-memory-card-choices/bus-interface-speed-standards-for-large-size-data-transfer/ |access-date=2025-05-28 |website=SD Association |language=en-US}}</ref> Equivalent card speed classes for a given bus mode are shown side by side.
{| class="wikitable"
|+
!Bus mode
! colspan="2" |Speed classes introduced at this bus mode
!Capacity types supported
|-
! rowspan="3" |Default
| colspan="2" |Speed Class 2 (C2)
| rowspan="4" |SDSC, SDHC, SDXC, SDUC
|-
| colspan="2" |Speed Class 4 (C4)
|-
|Speed Class 6 (C6)
|Video Speed Class 6 (V6)
|-
!High Speed
|Speed Class 10 (C10)
|Video Speed Class 10 (V10)
|-
! rowspan="2" |UHS-I
| colspan="2" |UHS Speed Class 1 (U1)
| rowspan="9" |SDHC, SDXC, SDUC
|-
|UHS Speed Class 3 (U3)
|Video Speed Class 30 (V30)
|-
! rowspan="2" |UHS-II
| colspan="2" |Video Speed Class 60 (V60)
|-
| colspan="2" |Video Speed Class 90 (V90)
|-
!UHS-III
| colspan="2" |No new labeled speed classes
|-
! rowspan="4" |SD Express (PCIe)
| colspan="2" |SD Express Speed Class 150 (E150)
|-
| colspan="2" |SD Express Speed Class 300 (E300)
|-
| colspan="2" |SD Express Speed Class 450 (E450)
|-
| colspan="2" |SD Express Speed Class 600 (E600)
|}
Note that a card will only have support at a given bus mode and card speed class level if it is explicitly labeled accordingly.  In addition, some SDSC cards do support the High Speed bus, but only at Speed Class 6 and below.

== Performance ratings ==
{| class="wikitable" style="float:right; text-align:center;"
|+Comparison of Application Performance Class ratings<ref>{{Cite web |date=2020-12-11 |title=Application Performance Class {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US |archive-date=3 November 2021 |archive-url=https://web.archive.org/web/20211103014547/https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |url-status=live }}</ref>
|-
! rowspan="2" | Rating
! colspan="2" | Minimum random [[IOPS]]
! rowspan="2" | Minimum sustained<br>sequential writing
|- 
! Read
! Write
|- 
| style="background:white" | {{Nowrap|Class 1 (A1)}}<br />[[File:SD App Performance 1.svg|x20px]]
| 1,500
| 500
| rowspan="2" |{{Nowrap|10 MB/s}}
|-
| style="background:white" | {{Nowrap|Class 2 (A2)}}<br />[[File:SD App Performance 2.svg|x20px]]
| 4,000
| 2,000
|}

'''Application Performance Class''' ratings were developed to address the increasing demand for SD memory cards capable of supporting both application storage and execution in mobile and embedded systems, while also supporting general-purpose data storage such as photos, videos, music, and documents. This need became more prominent with the growing use of SD cards for storing apps and application data, particularly following the introduction of Android's [[Adoptable Storage]] feature, which allows SD cards to function as internal (non-removable) storage.<ref>{{Cite web |title=Adoptable storage |url=https://source.android.com/docs/core/storage/adoptable |access-date=2025-04-12 |website=Android Open Source Project |language=en |archive-date=12 April 2025 |archive-url=https://web.archive.org/web/20250412032605/https://source.android.com/docs/core/storage/adoptable |url-status=live }}</ref>

Class A1, as defined in the SD Specification 5.1, requires a minimum of 1,500 input/output operations per second (IOPS) for reading and 500 IOPS for writing, using 4&nbsp;kB data blocks. Class A2, introduced in the SD Specification 6.0, raises these thresholds to 4,000 read and 2,000 write IOPS. A2 cards also depend on host driver support for features such as command queuing and write caching to achieve their specified performance; without this support, they operate at or above A1-level performance. Both A1 and A2 classes additionally require a minimum sustained sequential write speed of 10&nbsp;MB/s.<ref>"{{cite web |date=November 2016 |title=Application Performance Class: The new class of performance for applications on SD memory cards (SD 5.1) |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |url-status=live |archive-url=https://web.archive.org/web/20161123202004/https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |archive-date=2016-11-23 |access-date=2024-09-11 |website=sdcard.org}}</ref>

==Features==
===Card security===

====Commands to disable writes====
The host device can command the SD card to become read-only (to reject subsequent commands to write information to it). There are both reversible and irreversible host commands that achieve this.<ref>{{Cite web |last=By |date=2014-01-19 |title=The Tiniest SD Card Locker |url=https://hackaday.com/2014/01/18/the-tiniest-sd-card-locker/ |access-date=2023-01-20 |website=Hackaday |language=en-US}}</ref><ref>{{cite patent |country=US |number=7827370 |status=patent}}</ref>

====Write-protect notch====
[[File:SD card unlocked and locked.svg|thumb|Diagram showing an orange sliding write-protect switch in both the unlocked and locked positions]]
[[File:Vorderseite Sony Tough SF-M64T SDUHSII011CORRklein.png|thumb|upright|Sony Tough Series SD card, one of the few cards on the market without a sliding tab on the write protect notch]]

Most full-size SD cards have a mechanical write-protect switch, a sliding tab over a notch on the left side (viewed from the top, with the beveled corner on the right), that signals to the device to treat the card as read-only. Sliding the tab up (toward the contacts) sets the card to read/write; sliding it down sets it to read-only. However, the switch position is not detected by the card’s internal circuitry.<ref>{{Cite web|url=https://www.sdcard.org/downloads/pls/index.html|title=Simplified Specifications – SD Association, version 3.10, Part 1, Physical Layer, section 4.3.6" Write Protect Management"|website=sdcard.org|access-date=2019-04-11|archive-date=2019-04-11|archive-url=https://web.archive.org/web/20190411015937/https://www.sdcard.org/downloads/pls/index.html|url-status=live}}</ref> Therefore, some devices ignore it, while others allow overrides.{{citation needed|date=September 2023}}

MiniSD and microSD cards lack a built-in notch but can be used with adapters that include one. Cards without a notch are always writable; cards with preloaded content have a notch but no sliding tab.{{citation needed|date=September 2023}}

====Card password====
{{more citations needed|section=yes|date=September 2023}}
[[File:Sdadaptersandcards.jpg|thumb|MicroSD-to-SD adapter (left), microSD-to-miniSD adapter (middle), microSD card (right)]]

A host device can lock an SD card using a password of up to 16 bytes, typically supplied by the user.{{citation needed|date=September 2023}} A locked card interacts normally with the host device except that it rejects commands to read and write data.{{citation needed|date=September 2023}} A locked card can be unlocked only by providing the same password. The host device can, after supplying the old password, specify a new password or disable locking. Without the password (typically, in the case that the user forgets the password), the host device can command the card to erase all the data on the card for future re-use (except card data under DRM), but there is no way to gain access to the existing data.{{citation needed|date=September 2023}}

[[Windows Phone 7]] devices use SD cards designed for access only by the phone manufacturer or mobile provider. An SD card inserted into the phone underneath the battery compartment becomes locked "to the phone with an automatically generated key" so that "the SD card cannot be read by another phone, device, or PC".<ref>{{Cite web|url=https://support.microsoft.com/en-us/windows/windows-phone-7-3ebc303c-59c0-d367-3995-f258b184fabb|title=Windows Phone 7 – Microsoft Support|website=support.microsoft.com|access-date=2023-01-22|archive-date=2016-05-03|archive-url=https://web.archive.org/web/20160503105252/http://www.windowsphone.com/en-US/how-to/wp7/basics/copy-and-paste|url-status=live}}</ref> [[Symbian OS|Symbian]] devices, however, are some of the few that can perform the necessary low-level format operations on locked SD cards. It is therefore possible to use a device such as the [[Nokia N8]] to reformat the card for subsequent use in other devices.<ref>{{Cite web|url=https://www.engadget.com/2010/11/17/windows-phone-7s-microsd-mess-the-full-story-and-how-nokia-ca/|title=Windows Phone 7's microSD mess: the full story (and how Nokia can help you out of it)|website=Engadget|date=17 November 2010|access-date=13 October 2019|archive-date=8 August 2019|archive-url=https://web.archive.org/web/20190808215308/http://www.engadget.com/2010/11/17/windows-phone-7s-microsd-mess-the-full-story-and-how-nokia-ca/|url-status=live}}</ref>

===smartSD cards===
A smartSD memory card is a microSD card with an internal "[[secure element]]" that allows the transfer of ISO 7816 [[Smart card application protocol data unit|Application Protocol Data Unit]] commands to, for example, [[JavaCard]] applets running on the internal secure element through the SD bus.<ref>{{cite web |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Activating_New_Mobile_Services_and_Business_Models_With_smartSD_Memory_Cards_Revsied_11-3-2014.pdf |title=Activating New Mobile Services and Business Models with smartSD Memory cards |date=November 2014 |publisher=SD Association |access-date=2017-08-02 |archive-date=2016-12-23 |archive-url=https://web.archive.org/web/20161223213554/https://www.sdcard.org/downloads/pls/latest_whitepapers/Activating_New_Mobile_Services_and_Business_Models_With_smartSD_Memory_Cards_Revsied_11-3-2014.pdf |url-status=dead}}</ref>

Some of the earliest versions of microSD memory cards with secure elements were developed in 2009 by [[DeviceFidelity, Inc.]],<ref>{{cite web |url=https://www.nfcw.com/2009/11/11/32254/devicefidelity-launches-low-cost-microsd-based-nfc-solution/ |title=DeviceFidelity launches low cost microSD-based NFC solution |website=nfcw.com |last=Clark |first=Sarah |date=11 November 2009 |access-date=28 July 2021 |archive-date=4 March 2021 |archive-url=https://web.archive.org/web/20210304175751/https://www.nfcw.com/2009/11/11/32254/devicefidelity-launches-low-cost-microsd-based-nfc-solution/ |url-status=live}}</ref><ref>{{cite web |url=https://www.secureidnews.com/news-item/devicefidelity-rolls-out-microsd-payment-tool/ |title=DeviceFidelity rolls out microSD payment tool |website=SecureIDNews |date=10 November 2009 |access-date=28 July 2021 |archive-date=8 May 2021 |archive-url=https://web.archive.org/web/20210508014458/https://www.secureidnews.com/news-item/devicefidelity-rolls-out-microsd-payment-tool/ |url-status=live}}</ref> a pioneer in [[near-field communication]] (NFC) and [[mobile payments]], with the introduction of In2Pay and CredenSE products, later commercialized and certified for mobile contactless transactions by [[Visa Inc.|Visa]] in 2010.<ref>{{cite web |url=https://investor.visa.com/news/news-details/2010/Visa-and-DeviceFidelity-Collaborate-to-Accelerate-Adoption-of-Mobile-Contactless-Payments/default.aspx |title=Visa and DeviceFidelity Collaborate to Accelerate Adoption of Mobile Contactless Payments |website=visa.com |date=15 February 2010 |access-date=28 July 2021 |archive-date=19 September 2015 |archive-url=https://web.archive.org/web/20150919131031/http://investor.visa.com/news/news-details/2010/Visa-and-DeviceFidelity-Collaborate-to-Accelerate-Adoption-of-Mobile-Contactless-Payments/default.aspx |url-status=live}}</ref> DeviceFidelity also adapted the In2Pay microSD to work with the Apple iPhone using the iCaisse, and pioneered the first NFC transactions and mobile payments on an Apple device in 2010.<ref>{{cite web |url=https://www.engadget.com/2010-05-18-in2pay-is-the-name-of-visa-and-devicefidelitys-money-grubbing-i.html |title=In2Pay is the name of Visa and DeviceFidelity's money-grubbing iPhone case |website=Engadget |date=18 May 2010 |access-date=28 July 2021 |archive-date=26 January 2021 |archive-url=https://web.archive.org/web/20210126201901/https://www.engadget.com/2010-05-18-in2pay-is-the-name-of-visa-and-devicefidelitys-money-grubbing-i.html |url-status=live}}</ref><ref>{{cite web |url=https://www.youtube.com/watch?v=trHueSWx0-g |archive-url=https://ghostarchive.org/varchive/youtube/20211029/trHueSWx0-g| archive-date=2021-10-29|title=Device Fidelity's Amitaabh Mohortra Speaks about their micro NFC device for almost any phone |website=youtube.com |date=26 October 2013 |access-date=28 July 2021 |url-status=live}}{{cbignore}}</ref><ref>{{cite web |url=https://www.nfcw.com/2010/09/23/34489/devicefidelity-adds-nfc-microsd-support-for-iphone-4/ |title=DeviceFidelity adds NFC microSD support for iPhone 4 |last=Clark |first=Mike |website=nfcw.com |date=23 September 2010 |access-date=28 July 2021 |archive-date=19 January 2021 |archive-url=https://web.archive.org/web/20210119025901/https://www.nfcw.com/2010/09/23/34489/devicefidelity-adds-nfc-microsd-support-for-iphone-4/ |url-status=live}}</ref>

Various implementations of smartSD cards have been done for payment applications and secured authentication.<ref>{{cite web|url=http://www.sdcard.org/developers/overview/ASSD/smartsd|title=smartSD Memory Cards|publisher=SD Association|access-date=2016-02-23|archive-date=2015-07-08|archive-url=https://web.archive.org/web/20150708041012/http://www.sdcard.org/developers/overview/ASSD/smartsd/|url-status=live}}</ref><ref>{{cite web|url=http://nfctimes.com/news/microsd-vendor-announces-taiwanese-m-payment-trial-using-htc-nfc-phones|title=MicroSD Vendor Announces Taiwanese M-Payment Trial Using HTC NFC Phones|publisher=NFC Times|access-date=2016-02-23|archive-date=2016-04-27|archive-url=https://web.archive.org/web/20160427232346/http://nfctimes.com/news/microsd-vendor-announces-taiwanese-m-payment-trial-using-htc-nfc-phones|url-status=live}}</ref> In 2012 [[Good Technology]] partnered with DeviceFidelity to use microSD cards with secure elements for [[mobile identity]] and [[access control]].<ref>{{cite web |url=https://www.secureidnews.com/news-item/devicefidelitys-good-vault-provides-identity-and-access-solution-for-ios/ |title=DeviceFidelity's Good Vault provides identity and access solution for iOS |website=SecureIDNews |last=Hudson |first=Andrew |date=10 December 2012 |access-date=28 July 2021 |archive-date=23 October 2021 |archive-url=https://web.archive.org/web/20211023195556/https://www.secureidnews.com/news-item/devicefidelitys-good-vault-provides-identity-and-access-solution-for-ios/ |url-status=live}}</ref>

microSD cards with Secure Elements and NFC ([[near-field communication]]) support are used for mobile payments, and have been used in direct-to-consumer mobile wallets and mobile banking solutions, some of which were launched by major banks around the world, including [[Bank of America]], [[US Bank]] and [[Wells Fargo]],<ref>{{cite press release |url=https://www.businesswire.com/news/home/20130114005951/en/Datacard-Group-DeviceFidelity-U.S.-Bank-Announce-New |title=Datacard Group, DeviceFidelity and U.S. Bank Announce New Smart Card and Mobile Payment Program |publisher=Datacard Group |date=14 January 2013 |access-date=28 July 2021 |via=Businesswire |archive-date=20 August 2021 |archive-url=https://web.archive.org/web/20210820214158/https://www.businesswire.com/news/home/20130114005951/en/Datacard-Group-DeviceFidelity-U.S.-Bank-Announce-New |url-status=live}}</ref><ref>{{cite web |url=https://www.nfcw.com/2010/08/19/34339/bank-of-america-to-run-nfc-payments-trial-in-new-york/ |title=Bank of America to run NFC payments trial in New York |website=nfcw.com |last=Clark |first=Sarah |date=19 August 2010 |access-date=28 July 2021 |archive-date=25 January 2021 |archive-url=https://web.archive.org/web/20210125143142/https://www.nfcw.com/2010/08/19/34339/bank-of-america-to-run-nfc-payments-trial-in-new-york/ |url-status=live}}</ref><ref>{{Cite web |url=https://www.businesswire.com/news/home/20101206007176/en/Wells-Fargo-Roll-Mobile-Payments-Pilot-Visa |title=Wells Fargo to Roll Out Mobile Payments Pilot; Visa Demonstrating Capability at CARTES 2010 &#124; Business Wire |access-date=2020-10-14 |archive-date=2020-10-14 |archive-url=https://web.archive.org/web/20201014173430/https://www.businesswire.com/news/home/20101206007176/en/Wells-Fargo-Roll-Mobile-Payments-Pilot-Visa |url-status=dead}}</ref> while others were part of innovative new direct-to-consumer [[neobank]] programs such as [[moneto]], first launched in 2012.<ref>{{cite press release |url=https://www.prweb.com/releases/2012/1/prweb9086910.htm |archive-url=https://web.archive.org/web/20120113083550/http://www.prweb.com/releases/2012/1/prweb9086910.htm |url-status=dead |archive-date=January 13, 2012 |title=DeviceFidelity and SpringCard Launch moneto, the World's First Multi-Platform Mobile Wallet for iPhone and Android at CES |publisher=DeviceFidelity |date=10 January 2012 |access-date=28 July 2021 |via=Cision}}</ref><ref>{{cite web |url=https://www.nfcw.com/2012/09/11/317791/moneto-to-bring-nfc-payments-to-europe/ |title=Moneto to bring NFC payments to Europe |website=nfcw.com |last=Clark |first=Sarah |date=11 September 2012 |access-date=28 July 2021 |archive-date=25 January 2021 |archive-url=https://web.archive.org/web/20210125134752/https://www.nfcw.com/2012/09/11/317791/moneto-to-bring-nfc-payments-to-europe/ |url-status=live}}</ref><ref>{{cite web|url=http://www.rfid-ready.com/201403038507/garanti-bank-deploys-nfc-services-on-microsd.html|title=Garanti Bank deploys NFC services on microSD|publisher=RFID Ready|access-date=2016-02-23|archive-date=2017-02-02|archive-url=https://web.archive.org/web/20170202124458/http://www.rfid-ready.com/201403038507/garanti-bank-deploys-nfc-services-on-microsd.html|url-status=dead}}</ref><ref>{{cite web|url=http://www.nfcworld.com/2012/10/31/320843/devicefidelity-launches-new-range-of-nfc-microsd-devices/|title=DeviceFidelity launches new range of NFC microSD devices|publisher=NFC World+|date=2012-10-31|access-date=2016-02-23|archive-date=2016-04-20|archive-url=https://web.archive.org/web/20160420165354/http://www.nfcworld.com/2012/10/31/320843/devicefidelity-launches-new-range-of-nfc-microsd-devices/|url-status=live}}</ref>

microSD cards with Secure Elements have also been used for secure [[voice encryption]] on mobile devices, which allows for one of the highest levels of security in person-to-person voice communications.<ref>{{cite web |url=https://koolspan.com/iphone_devicefidelity/ |title=iPhone Voice Encryption from KoolSpan and DeviceFidelity |website=koolspan.com |date=11 March 2013 |access-date=28 July 2021 |archive-date=27 January 2021 |archive-url=https://web.archive.org/web/20210127060537/https://koolspan.com/iphone_devicefidelity/ |url-status=dead}}</ref> Such solutions are heavily used in intelligence and security.

In 2011, [[HID Global]] partnered with [[Arizona State University]] to launch campus access solutions for students using microSD with Secure Element and [[MiFare]] technology provided by [[DeviceFidelity, Inc.]]<ref>{{cite web |url=https://www.cr80news.com/news-item/arizona-students-first-to-trial-mobile-phones-with-nfc-for-door-access/ |title=Arizona students first to trial mobile phones with NFC for door access |work=CR80 News |last=Corum |first=Chris |date=14 September 2011 |access-date=28 July 2021 |archive-date=6 November 2021 |archive-url=https://web.archive.org/web/20211106083657/https://www.cr80news.com/news-item/arizona-students-first-to-trial-mobile-phones-with-nfc-for-door-access/ |url-status=live}}</ref><ref>{{cite web |url=https://www.youtube.com/watch?v=d4NmYdMAAHU | archive-url=https://ghostarchive.org/varchive/youtube/20211029/d4NmYdMAAHU| archive-date=2021-10-29|title=Case Study: Mobile Access Pilot at Arizona State University |website=youtube.com |date=14 October 2011 |access-date=28 July 2021 |url-status=live}}{{cbignore}}</ref> This was the first time regular mobile phones could be used to open doors without need for electronic access keys.

===<span class="anchor" id="Integrated Wi-Fi"></span> Vendor enhancements===
 {{multiple image
 | SD cards with integrated Wi-Fi
 | perrow      = 2
 | total_width = 390
 | image1      = Eye-Fi Wifi Card.jpg
 | caption1    = Eye-Fi Mobi 16&nbsp;GB
 | image2      = FlashAir 014 (15247275839) (cropped).jpg
 | caption2    = Toshiba FlashAir 16&nbsp;GB
 | image3      = Pqi-air-card 開箱 (8536928274) (cropped).jpg
 | caption3    = PQI air card 4&nbsp;GB
 | image4      = Transcend WiFi SD-Card.jpg
 | caption4    = Transcend Wi-Fi 16&nbsp;GB
 }}
[[File:USB-SD-Cards.jpg|thumb|SD cards with dual interfaces: SD and [[USB]]]]

Vendors have sought to differentiate their products in the market through various vendor-specific features:
* '''Integrated [[Wi-Fi]]''' – Several companies produce SD cards with built-in Wi-Fi transceivers supporting static security (WEP 40/104/128, WPA-PSK and WPA2-PSK). The card lets any digital camera with an SD slot transmit captured images over a wireless network, or store the images on the card's memory until it is in range of a wireless network. Examples include: [[Eye-Fi]] / [[SanDisk Eye-Fi|SanDisk]], [[Transcend Wi-Fi]], [[Toshiba FlashAir]], [[Trek Flucard]], [[PQI Air Card]] and [[LZeal ez Share]].<ref>{{cite web |url=http://www.eye.fi/ |title=Eye-Fi |access-date=2010-08-22 |url-status=dead |archive-url=http://webarchive.loc.gov/all/20100826002041/http%3A//www.eye.fi/ |archive-date=2010-08-26}}</ref> Some models [[Geotagging|geotag]] their pictures.
* '''Pre-loaded content''' – In 2006, SanDisk announced [[Gruvi]], a microSD card with extra digital rights management features, which they intended as a medium for publishing content. SanDisk again announced pre-loaded cards in 2008, under the [[slotMusic]] name, this time not using any of the DRM capabilities of the SD card.<ref>{{cite web |last=Robson |first=Wayde |url=http://www.audioholics.com/news/industry-news/sandisk-slotmusic |title=AudioHolics |date=22 September 2008 |publisher=AudioHolics |access-date=2014-01-02 |archive-date=2013-06-02 |archive-url=https://web.archive.org/web/20130602015817/http://www.audioholics.com/news/industry-news/sandisk-slotmusic |url-status=live}}</ref> In 2011, SanDisk offered various collections of 1000 songs on a single slotMusic card for about $40,<ref>{{cite web|url=http://www.sandisk.com/consumer-products/slotradio|title=slotRadio|publisher=SanDisk|access-date=2011-11-27|archive-date=2011-11-24|archive-url=https://web.archive.org/web/20111124105916/http://www.sandisk.com/consumer-products/slotradio|url-status=live}}</ref> now restricted to compatible devices and without the ability to copy the files.
* '''Integrated USB connector''' – The [[SanDisk]] '''SD Plus''' product can be plugged directly into a [[USB]] port without needing a USB card reader.<ref>{{Citation |url=https://www.theregister.co.uk/2005/07/25/review_sandisk_ultra_ii_sd_plus/ |title=SanDisk Ultra II SD Plus USB/SD card |newspaper=The Register |place=[[United Kingdom|UK]] |date=2005-07-25 |access-date=2024-09-11 |archive-date=2019-08-08 |archive-url=https://web.archive.org/web/20190808091122/https://www.theregister.co.uk/2005/07/25/review_sandisk_ultra_ii_sd_plus/ |url-status=live}}</ref> Other companies introduced comparable products, such as the '''Duo SD''' product of [[OCZ Technology]] and the '''3 Way''' (microSDHC, SDHC and USB) product of [[A-DATA]], which was available in 2008 only.
* '''Different colors''' – SanDisk has used various colors of plastic or adhesive label, including a "gaming" line in translucent plastic colors that indicated the card's capacity. In 2006, the first 256MB microSD to use color-coded cards by Kingmax, which later other brands (e.g., SanDisk, Kioxia) had been implementing to this day.
* '''Integrated display''' – In 2006, ADATA announced a '''Super Info SD''' card with a digital display that provided a two-character label and showed the amount of unused memory on the card.<ref>{{cite web |url=http://www.techpowerup.com/reviews/AData/ADATASuperInfoSD/ |title=A-DATA Super Info SD Card 512MB |publisher=Tech power up |date=2007-02-20 |access-date=2011-12-30 |archive-date=2012-05-18 |archive-url=https://web.archive.org/web/20120518161342/http://www.techpowerup.com/reviews/AData/ADATASuperInfoSD/ |url-status=live}}</ref>

===SDIO cards===
{{more citations needed|section=yes|date=September 2023}}
[[File:SDIO Vector.svg|thumb|upright=0.65|Secure Digital Input Output (SDIO) mark]]
[[File:HP PhotoSmart SDIO Kamera (cropped).jpg|thumb|upright|Camera using the SDIO interface to connect to some HP [[iPAQ]] devices]]

A SDIO (Secure Digital Input Output) card is an extension of the SD specification to cover I/O functions. SDIO cards are only fully functional in host devices designed to support their input-output functions (typically PDAs like the [[Palm Treo]], but occasionally laptops or mobile phones).{{citation needed|date=September 2023}} These devices can use the SD slot to support [[GPS]] receivers, [[modem]]s, [[barcode reader]]s, [[FM radio]] tuners, TV tuners, [[RFID]] readers, [[digital camera]]s and interfaces to [[Wi-Fi]], [[Bluetooth]], [[Ethernet]] and [[IrDA]]. Many other SDIO devices have been proposed, but it is now more common for I/O devices to connect using the USB interface.{{citation needed|date=September 2023}}

SDIO cards support most of the memory commands of SD cards. SDIO cards can be structured as eight logical cards, although currently, the typical way that an SDIO card uses this capability is to structure itself as one I/O card and one memory card.{{citation needed|date=September 2023}}

The SDIO and SD interfaces are mechanically and electrically identical. Host devices built for SDIO cards generally accept SD memory cards without I/O functions. However, the reverse is not true, because host devices need suitable drivers and applications to support the card's I/O functions. For example, an HP SDIO camera usually does not work with PDAs that do not list it as an accessory. Inserting an SDIO card into any SD slot causes no physical damage nor disruption to the host device, but users may be frustrated that the SDIO card does not function fully when inserted into a seemingly compatible slot. (USB and Bluetooth devices exhibit comparable compatibility issues, although to a lesser extent thanks to standardized [[Class driver|USB device classes]] and [[Bluetooth profiles]].){{citation needed|date=September 2023}}

The [[#SDIO|SDIO]] family comprises Low-Speed and Full-Speed cards. Both types of SDIO cards support [[Serial Peripheral Interface]] (SPI) and one-bit SD bus types. Low-Speed SDIO cards are allowed to also support the four-bit SD bus; Full-Speed SDIO cards are required to support the four-bit SD bus. To use an SDIO card as a "combo card" (for both memory and I/O), the host device must first select four-bit SD bus operation. Two other unique features of Low-Speed SDIO are a maximum clock rate of 400&nbsp;kHz for all communications, and the use of Pin 8 as "interrupt" to try to initiate dialogue with the host device.<ref name="SDIOspec">{{cite web |url=https://www.sdcard.org/developers/overview/sdio/sdio_spec/ |title=Simplified Version of SDIO CARD SPEC |publisher=SD Association |access-date=2011-12-09 |archive-date=2015-04-15 |archive-url=https://web.archive.org/web/20150415230526/https://www.sdcard.org/developers/overview/sdio/sdio_spec/ |url-status=dead}}</ref>

===Compatibility===
Host devices that comply with newer versions of the specification provide [[backward compatibility]] and accept older SD cards.<ref name="sdcard.org"/> For example, SDXC host devices accept all previous families of SD memory cards, and SDHC host devices also accept standard SD cards.

Older host devices generally do not support newer card formats, and even when they might support the bus interface used by the card,<ref name=sdcard_using_sdxc/> there are several factors that arise:
* A newer card may offer greater [[#Cpcty|capacity]] than the host device can handle (over 4&nbsp;GB for SDHC, over 32&nbsp;GB for SDXC).
* A newer card may use a [[#Filesys|file system]] the host device cannot navigate ([[FAT32]] for SDHC, [[exFAT]] for SDXC)
* Use of an SDIO card requires the host device be designed for the input/output functions the card provides.
* The hardware interface of the card was changed starting with the version 2.0 (new high-speed bus clocks, redefinition of [[#Storage capacity calculations|storage capacity bits]]) and [[#SDHC|SDHC]] family (ultra-high speed (UHS) bus)
* UHS-II has physically more pins but is backwards compatible to UHS-I and non-UHS for both slot and card.<ref name="sda_bus_speed"/>
* Some vendors produced SDSC cards above 1&nbsp;GB before the SDA had standardized a method of doing so.

{| class="wikitable"
|+ SD compatibility table
! {{Diagonal split header 2|Slot|Card}}
! scope="col" | SDSC
! scope="col" | SDHC
! scope="col" | SDHC<br />UHS
! scope="col" | SDXC
! scope="col" | SDXC<br />UHS
! scope="col" | SDIO
|-
! style="text-align:left;" | SDSC
| {{Partial}}{{Efn|name=sdsccompat|See [[#Storage_capacity_and_compatibilities|discussion about storage capacity and compatibilities]].}} || {{Partial|FAT16, < 4&nbsp;GB}}{{Efn|name=sdsccompat}} || {{Partial|FAT16, < 4&nbsp;GB}}{{Efn|name=sdsccompat}} || {{No}} || {{No}} || {{No}}
|-
! style="text-align:left;" | SDHC
| {{Yes}} || {{Yes}} || {{good|In non-UHS mode}} || {{Partial|FAT32}} || {{Partial|FAT32 in non-UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDHC UHS
| {{good|In non-UHS mode}} || {{good|In non-UHS mode}} || {{Yes|In UHS mode}} || {{Partial|FAT32 in non-UHS mode}} || {{Partial|FAT32 in UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDXC
| {{Yes}} || {{Yes}} || {{good|In non-UHS mode}} || {{Yes}} || {{good|In non-UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDXC UHS
| {{good|In non-UHS mode}} || {{good|In non-UHS mode}} || {{Yes|In UHS mode}} || {{good|In non-UHS mode}}|| {{Yes|In UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDIO
| {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{Yes}}
|}

==Markets==
[[File:Micro-SD-Kartenleser der Nintendo Switch 20230405 HOF09182 RAW-Export.png|thumb|alt=This image shows an internal MicroSD card reader, as it can be found in game consoles like the Nintendo Switch|An internal microSD card reader, taken from a [[Nintendo Switch]]]]
Due to their compact size, Secure Digital cards are used in many consumer electronic devices, and have become a widespread means of storing several gigabytes of data in a small size. Devices in which the user may remove and replace cards often, such as [[digital camera]]s, [[camcorder]]s and [[video game console]]s, tend to use full-sized cards. Devices in which small size is paramount, such as [[mobile phone]]s, [[action camera]]s such as the [[GoPro#HERO cameras|GoPro Hero]] series, and [[Unmanned aerial vehicle|camera drones]], tend to use microSD cards.<ref name="FB">{{cite web |title=4 Features and Benefits of a Micro SD Transflash Memory Card – Steve's Digicams |url=http://www.steves-digicams.com/knowledge-center/how-tos/photo-accessories/4-features-and-benefits-of-a-micro-sd-transflash-memory-card.html |website=steves-digicams.com |access-date=2020-11-30 |archive-date=2014-01-17 |archive-url=https://web.archive.org/web/20140117070452/https://www.steves-digicams.com/knowledge-center/how-tos/photo-accessories/4-features-and-benefits-of-a-micro-sd-transflash-memory-card.html |url-status=live }}</ref><ref name="AD">{{cite web |title=Advantages and Disadvantages of Memory Cards |url=https://www.engadget.com/2016-10-11-advantages-and-disadvantages-of-memory-cards.html |website=Engadget |language=en |date=2016-10-11 |access-date=2020-11-30 |archive-date=2020-10-28 |archive-url=https://web.archive.org/web/20201028124543/https://www.engadget.com/2016-10-11-advantages-and-disadvantages-of-memory-cards.html |url-status=dead}}</ref>

=== Mobile phones ===
The microSD card has helped propel the smartphone market by giving both manufacturers and consumers greater flexibility and freedom.

While [[cloud storage]] depends on stable internet connection and sufficiently voluminous [[data plan]]s, memory cards in mobile devices provide location-independent and [[privacy|private]] storage expansion with much higher transfer rates and no [[network delay]], enabling applications such as [[photography]] and [[video recording]]. While data stored internally on [[Brick (electronics)|bricked device]]s is [[data loss|inaccessible]], data stored on the memory card can be salvaged and accessed externally by the user as [[mass storage]] device. A benefit over [[USB on the go]] storage expansion is uncompromised [[ergonomy]]. The usage of a memory card also protects the mobile phone's non-replaceable internal storage from weardown from heavy applications such as excessive camera usage and portable [[FTP server]] hosting over [[WiFi Direct]]. Due to the [[#2009–2019: SDXC|technical development]] of memory cards, users of existing mobile devices are able to expand their storage further and priceworthier with time.<ref>{{cite web |title=Understanding Life Expectancy of Flash Storage |url=https://www.ni.com/en-nz/support/documentation/supplemental/12/understanding-life-expectancy-of-flash-storage.html |website=ni.com |language=en |date=2020-07-23 |access-date=2020-11-30 |archive-date=2023-09-13 |archive-url=https://web.archive.org/web/20230913042854/https://www.ni.com/en-nz/support/documentation/supplemental/12/understanding-life-expectancy-of-flash-storage.html |url-status=live }}</ref><ref>{{cite web |title=12 Advantages & Disadvantages of Using SD Card in Smartphone |url=https://www.datanumen.com/blogs/12-advantages-disadvantages-using-sd-card-smartphone/ |website=Data Recovery Blog |date=23 November 2017 |access-date=30 November 2020 |archive-date=30 November 2020 |archive-url=https://web.archive.org/web/20201130140603/https://www.datanumen.com/blogs/12-advantages-disadvantages-using-sd-card-smartphone/ |url-status=live }}</ref><ref>{{cite web |last=Ali |first=Mudassar |title=Benefits of Using an SD Card |url=https://medium.com/@mudassarali143/benefits-of-using-an-sd-card-fc9f3e477e05 |website=Medium |language=en |date=27 November 2018 |access-date=30 November 2020 |archive-date=30 November 2020 |archive-url=https://web.archive.org/web/20201130135021/https://medium.com/@mudassarali143/benefits-of-using-an-sd-card-fc9f3e477e05 |url-status=live }}</ref>

Recent versions of major operating systems such as [[Windows Mobile]] and [[Android (operating system)|Android]] allow applications to run from microSD cards, creating possibilities for new usage models for SD cards in mobile computing markets, as well as clearing available internal storage space.<ref>{{cite web|url=http://www.androidcentral.com/inside-marshmallow-adoptable-storage|title=Inside Marshmallow: Adoptable storage|publisher=Android Central|date=2015-11-15|access-date=2016-02-23|archive-date=2016-02-21|archive-url=https://web.archive.org/web/20160221152352/http://www.androidcentral.com/inside-marshmallow-adoptable-storage|url-status=live}}</ref>

SD cards are not the most economical solution in devices that need only a small amount of non-volatile memory, such as station presets in small radios. They may also not present the best choice for applications that require higher storage capacities or speeds as provided by other flash card standards such as [[CompactFlash]]. These limitations may be addressed by evolving memory technologies, such as the new SD 7.0 specifications which allow storage capabilities of up to 128&nbsp;TB.{{efn|name="here, 1&nbsp;TB = 1024"}}<ref>{{cite web |url=https://www.sdcard.org/consumers/choices/speed_class/index.html |title=Speed Class Standards for Video Recording |website=SD Association |access-date=21 November 2018 |archive-date=7 April 2016 |archive-url=https://web.archive.org/web/20160407123207/https://www.sdcard.org/consumers/choices/speed_class/index.html |url-status=live }}</ref>

Many personal computers of all types, including tablets and mobile phones, use SD cards, either through built-in slots or through an active electronic adapter. Adapters exist for the [[PC card]], ExpressBus, [[USB]], [[FireWire]] and the [[parallel port|parallel printer port]]. Active adapters also let SD cards be used in devices designed for other formats, such as [[CompactFlash]]. The [[FlashPath]] adapter lets SD cards be used in a [[floppy disk]] drive.

Some devices such as the [[Samsung Galaxy Fit (smartphone)|Samsung Galaxy Fit]] (2011) and [[Samsung Galaxy Note 8.0]] (2013) have an SD card compartment located externally and accessible by hand, while it is located under the battery cover on other devices. More recent mobile phones use a pin-hole ejection system for the tray which houses both the memory card and [[SIM card]].

===Counterfeits===
[[File:Samsung Pro 64gb micro-SDXC original and falsification front and back.jpg|thumb|[[Samsung Electronics|Samsung]] Pro 64&nbsp;GB microSDXC original (left) and counterfeit (right): The counterfeit claims to have 64&nbsp;GB in capacity, but only 8&nbsp;GB (Class 4 speed) are usable: When trying to write more than 8&nbsp;GB, [[data loss]] occurs. Also used for [[SanDisk]] 64&nbsp;GB fakes.]]
[[File:Decapsulated microSD memory card lineup-genuine, questionable, and fake-counterfeit.jpg|thumb|Images of genuine, questionable and counterfeit microSD (Secure Digital) cards before and after decapsulation. Details [http://www.bunniestudios.com/blog/?page_id=1022 at source], photo by [[Andrew Huang (hacker)|Andrew Huang]]]]

Commonly found on the market are mislabeled or counterfeit Secure Digital cards that report a fake capacity or run slower than labeled.<ref>{{cite web |last=bunnie |title=On MicroSD Problems |url=https://www.bunniestudios.com/blog/?page_id=1022 |access-date=2024-01-22 |website=bunniestudios.com |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911013533/https://www.bunniestudios.com/blog/on-microsd-problems/ |url-status=live }}</ref><ref name="c't2007">{{cite web |last=Schnurer |first=Georg |title=Gefälschte SD-Karten |language=de |trans-title=Fake SD-cards |publisher=Heise mobile – c't magazin für computertechnik |date=2007-02-28 |url=http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |access-date=2013-06-07 |archive-date=2013-06-23 |archive-url=https://web.archive.org/web/20130623055703/http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |url-status=dead }}</ref><ref name="c't2013-häufiges">{{cite web |url=http://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |title=Smartphones wählerisch bei microSDHC-Karten |publisher=Heise mobile – c't magazin für computertechnik |date=2013-03-18 |access-date=2013-06-09 |last=Feddern |first=Boi |language=de |archive-date=2019-01-01 |archive-url=https://web.archive.org/web/20190101010525/https://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |url-status=live }}</ref> Software tools exist to check and detect [[USB flash drive#Counterfeit products|counterfeit products]],<ref name="h2testw">{{cite web |title=H2testw heise Download |language=de |url=https://www.heise.de/download/product/h2testw-50539 |access-date=2016-11-26 |archive-date=2016-11-26 |archive-url=https://web.archive.org/web/20161126111115/https://www.heise.de/download/product/h2testw-50539 |url-status=live}}</ref><ref name="f3">{{cite web |title=F3 by Digirati |url=https://oss.digirati.com.br/f3/ |access-date=2016-11-26 |archive-date=2016-11-24 |archive-url=https://web.archive.org/web/20161124080508/http://oss.digirati.com.br/f3/ |url-status=live}}</ref><ref>{{cite web |url=https://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 |archive-date=2023-06-24 |archive-url=https://web.archive.org/web/20230624000054/https://www.usbdev.ru/articles/detect_controller/ |url-status=live }}</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"] {{Webarchive|url=https://web.archive.org/web/20110109230403/http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ |date=2011-01-09 }}, fixfakeflash.wordpress.com, retrieved November 16, 2010</ref>

Detection of counterfeit cards usually involves copying files with [[random data]] to the SD card until the card's capacity is reached, and copying them back. The files that were copied back can be tested either by comparing checksums (e.g. [[Md5sum|MD5]]), or trying to [[Data compression|compress]] them. The latter approach leverages the fact that counterfeited cards let the user read back files, which then consist of easily compressible uniform data (for example, repeating [[0xFF]]s).

===Digital cameras===
[[File:Pentax K10D with SanDiskSD card.jpg|thumb|SD card in a [[DSLR]] camera]]

Secure Digital memory cards can be used in Sony [[XDCAM]] EX [[camcorder]]s with an adapter.<ref>{{cite web |url=http://pro.sony.com/bbsc/ssr/micro-xdcamexsite/cat-accessories/product-MEADSD01/ |title=MEAD-SD01 SDHC card adapter (Sony) |publisher=Pro.sony.com |access-date=2014-01-02 |archive-date=2017-06-29 |archive-url=https://web.archive.org/web/20170629034942/http://pro.sony.com/bbsc/ssr/micro-xdcamexsite/cat-accessories/product-MEADSD01/ |url-status=live }}</ref>

===Personal computers===
Although many [[personal computer]]s accommodate SD cards as an auxiliary storage device using a built-in slot, or can accommodate SD cards by means of a USB adapter, SD cards cannot be used as the primary [[hard disk]] through the onboard ATA controller, because none of the SD card variants support ATA signalling. Primary [[hard disk]] use requires a separate SD host controller<ref>{{cite web |url=http://www.embeddedarm.com/products/board-detail.php?product=TS-7800 |title=TS-7800 Embedded |publisher=Embeddedarm.com |access-date=2010-08-22 |archive-date=2015-02-15 |archive-url=https://web.archive.org/web/20150215021402/http://www.embeddedarm.com/products/board-detail.php?product=TS-7800 |url-status=dead }}</ref> or an SD-to-CompactFlash converter. However, on computers that support [[bootstrapping]] from a USB interface, an SD card in a USB adapter can be the boot disk, provided it contains an operating system that supports USB access once the bootstrap is complete.

In [[laptop]] and [[tablet computer]]s, memory cards in an integrated [[memory card reader]] offer an [[ergonomy|ergonomic]]al benefit over USB [[flash drive]]s, as the latter sticks out of the device, and the user would need to be cautious not to bump it while transporting the device, which could damage the USB port. Memory cards have a unified shape and do not reserve a USB port when inserted into a computer's dedicated card slot.

Since late 2009, newer [[Apple Inc.|Apple]] computers with installed SD card readers have been able to boot in [[macOS]] from SD storage devices, when properly formatted to [[HFS Plus|Mac OS Extended]] file format and the default partition table set to [[GUID Partition Table]].<ref>{{cite web |url=http://support.apple.com/kb/HT3553 |title=About the SD and SDXC card slot |publisher=Support.apple.com |date=2013-06-08 |access-date=2013-11-13 |archive-date=2011-09-03 |archive-url=https://web.archive.org/web/20110903100124/http://support.apple.com/kb/HT3553 |url-status=live }}</ref>

SD cards are increasing in usage and popularity among owners of [[vintage computer]]s like [[Atari 8-bit computers]]. For example SIO2SD ([[Atari SIO|SIO]] is an Atari port for connecting external devices) is used nowadays. Software for an 8-bit Atari may be included on one SD card that may have less than 4–8&nbsp;GB of disk size (2019).<ref>{{Cite web|url=https://retrohax.net/sio2sd-for-atari/|title=SIO2SD for 8-bit Atari|date=May 9, 2016|access-date=October 13, 2019|archive-date=October 13, 2019|archive-url=https://web.archive.org/web/20191013042823/https://retrohax.net/sio2sd-for-atari/|url-status=live}}</ref>

===Embedded systems===
[[File:Arduino Ethernet Shield (pre-production sample).jpg|thumb|A shield ([[daughterboard]]) that gives [[Arduino]] prototyping microprocessors access to SD cards]]

In 2008, the SDA specified Embedded SD, "leverag[ing] well-known SD standards" to enable non-removable SD-style devices on printed circuit boards.<ref>{{cite web|title=Embedded SD|publisher=SD Association|url=http://www.sdcard.org/developers/overview/embedded_sd/|access-date=2011-11-30|archive-date=2011-11-21|archive-url=https://web.archive.org/web/20111121065447/https://www.sdcard.org/developers/overview/embedded_sd/|url-status=live}}</ref> However this standard was not adopted by the market while the [[MultiMediaCard|MMC]] standard became the de facto standard for embedded systems. SanDisk provides such embedded memory components under the iNAND brand.<ref>{{cite web|title=iNAND Embedded Flash Drives|publisher=SanDisk|url=http://www.sandisk.com/business-solutions/inand-embedded-flash-drives|access-date=2011-11-30|archive-date=2011-12-25|archive-url=https://web.archive.org/web/20111225022347/http://www.sandisk.com/business-solutions/inand-embedded-flash-drives|url-status=live}}</ref>

While some modern [[microcontroller]]s integrate SDIO hardware which uses the faster proprietary four-bit SD bus mode, almost all modern microcontrollers at least have [[Serial Peripheral Interface Bus|SPI]] units that can interface to an SD card operating in the slower one-bit SPI bus mode. If not, SPI can also be emulated by [[bit banging]] (e.g. a SD card slot [[soldered]] to a [[Linksys]] [[WRT54G|WRT54G-TM]] router and wired to [[General-purpose input/output|GPIO]] pins using [[DD-WRT]]'s [[Linux kernel]] achieved only {{Nowrap|1.6 [[Mbit/s]]}} throughput).<ref>{{cite web |url=http://www.dd-wrt.com/wiki/index.php/Linksys_WRT54G-TM_SD/MMC_mod |title=Linksys WRT54G-TM SD/MMC mod – DD-WRT Wiki |publisher=Dd-wrt.com |date=2010-02-22 |access-date=2010-08-22 |archive-date=2010-09-01 |archive-url=https://web.archive.org/web/20100901020001/http://www.dd-wrt.com/wiki/index.php/Linksys_WRT54G-TM_SD/MMC_mod |url-status=live }}</ref>

===Music distribution===
Prerecorded microSDs have been used to commercialize music under the brands [[slotMusic]] and [[slotRadio]] by [[SanDisk]] and [[Astell & Kern#Mastering Quality Sound (MQS)|MQS]] by [[Astell & Kern]].

==Technical details==
{{More citations needed|section|date=September 2023}}
{{multiple image
| direction = vertical
| width     = 175
| header    = microSD card and standard SD card adapter
| image1    = SD card adapter.jpg
| image2    = SD card adapters.jpg
}}

===<span class="anchor" id="Physical size"></span>Physical size===
{{More citations needed|section|date=September 2023}}
The SD card specification defines three physical sizes. The SD and SDHC families are available in all three sizes, but the SDXC and SDUC families are not available in the mini size, and the SDIO family is not available in the micro size. Smaller cards are usable in larger slots through use of a passive adapter.

====Standard====
[[File:MicroSD MemoryCard 002.jpg|thumb|upright|Size comparison of families: SD (blue), miniSD (green), microSD (red)]]
* SD (SDSC), SDHC, SDXC, SDIO, SDUC
* {{Nowrap|{{cvt|32|x|24|x|2.1|mm|frac=64}}}}
* {{Nowrap|{{cvt|32|x|24|x|1.4|mm|frac=64}}}} (as thin as MMC) for '''Thin SD''' (rare)

====<span class="anchor" id="MiniSD"></span>MiniSD====
* miniSD, miniSDHC, miniSDIO
* {{Nowrap|{{cvt|21.5|x|20|x|1.4|mm|frac=64}}}}

====<span class="anchor" id="microSD"></span> microSD====
The micro form factor is the smallest SD card format.<ref name="sdcard_choices">{{cite web|title=About|publisher=SD Association|url=https://www.sdcard.org/consumers/choices/|access-date=2011-05-02|archive-date=2011-11-21|archive-url=https://web.archive.org/web/20111121065042/https://www.sdcard.org/consumers/choices/|url-status=live}}</ref>
* microSD, microSDHC, microSDXC, microSDUC
* {{Nowrap|{{cvt|15|x|11|x|1|mm|frac=64}}}}

===Transfer modes===
{{More citations needed|section|date=September 2023}}

Cards may support various combinations of the following bus types and transfer modes. The SPI bus mode and one-bit SD bus mode are mandatory for all SD families, as explained in the next section. Once the host device and the SD card negotiate a bus interface mode, the usage of the numbered pins is the same for all card sizes.
* '''SPI bus mode:''' [[Serial Peripheral Interface Bus]] is primarily used by embedded [[microcontroller]]s. This bus type supports only a 3.3-volt interface. This is the only bus type that does not require a host license.{{Citation needed|date=August 2019}}
* '''One-bit SD bus mode:''' Separate command and data channels and a proprietary transfer format.
* '''Four-bit SD bus mode:''' Uses extra pins plus some reassigned pins. This is the same protocol as the one-bit SD bus mode which uses one command and four data lines for faster data transfer. All SD cards support this mode. UHS-I and UHS-II require this bus type.
* '''Two differential lines SD UHS-II mode:''' Uses two [[low-voltage differential signaling]] interfaces to transfer commands and data. UHS-II cards include this interface in addition to the SD bus modes.

The physical interface comprises 9 pins, except that the miniSD card adds two unconnected pins in the center and the microSD card omits one of the two V<sub>SS</sub> (Ground) pins.<ref>{{cite web |url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |title=SD Part 1, Physical Layer Simplified Specification, Version 4.10 |access-date=2014-01-02 |url-status=dead |archive-url=https://web.archive.org/web/20131202232415/https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |archive-date=2013-12-02 }}</ref>

[[File:MMC-SD-miniSD-microSD-Color-Numbers-Names.gif|thumb|upright|Official pin numbers for each card type (top to bottom): [[MultiMediaCard|MMC]], SD, miniSD, microSD. This shows the evolution from the older MMC, on which SD is based. NOTE: This drawing does not show 8 new UHS-II contacts that were added in spec 4.0.]]

{| class="wikitable" style="text-align:center"
|+ SPI bus mode
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| 1 ||1 ||1 ||2 ||nCS ||I ||PP ||style="text-align:left"|SPI Card Select [CS] (Negative logic)
|-
| 2 ||2 ||2 ||3 ||DI ||I ||PP ||style="text-align:left"|SPI Serial Data In [MOSI]
|-
| 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|SPI Serial Clock [SCLK]
|-
| 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 7 ||7 ||7 ||7 ||DO ||O ||PP ||style="text-align:left"|SPI Serial Data Out [MISO]
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative logic)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

{| class="wikitable" style="text-align:center"
|+ One-bit SD bus mode
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| 1 ||1 ||1 ||2 ||CD ||I/O ||. ||style="text-align:left"|Card detection (by host) and<br />non-SPI mode detection (by card)
|-
| 2 ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response
|-
| 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock
|-
| 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 7 ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative Logic)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

{| class="wikitable" style="text-align:center"
|+ Four-bit SD bus mode
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| . ||1 ||1 ||2 ||DAT3 ||I/O ||PP ||style="text-align:left"|SD Serial Data 3
|-
| . ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response
|-
| . ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| . ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| . ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock
|-
| . ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| . ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||DAT1<br />nIRQ ||I/O<br />O ||PP<br />OD ||style="text-align:left"|SD Serial Data 1 (memory cards)<br />Interrupt Period (SDIO cards share pin via protocol)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||DAT2 ||I/O ||PP ||style="text-align:left"|SD Serial Data 2
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

Notes:
# Direction is relative to card. I = Input, O = Output.
# PP = [[Push–pull output|Push-Pull]] logic, OD = [[Open collector|Open-Drain]] logic.
# S = [[IC power supply pin|Power Supply]], NC = Not Connected (or [[Pull-up resistor|logical high]]).

===Interface===
[[File:Sd insides.png|thumb|Inside a 512&nbsp;MB SD card: [[NAND flash]] chip that holds the data (bottom) and [[SD controller]] (top)]]
[[File:SD-extreMEmory 2GB alt innen.jpg|thumb|upright|Inside a 2&nbsp;GB SD card: two [[NAND flash]] chips (top and middle), SD controller chip (bottom)]]
[[File:Pretec 16GB SDHC without cover 20090420.jpg|thumb|upright|Inside a 16&nbsp;GB SDHC card]]

====Command interface====
SD cards and host devices initially communicate through a [[synchronous]] one-bit interface, where the host device provides a clock signal that strobes single bits in and out of the SD card. The host device thereby sends 48-bit commands and receives responses. The card can signal that a response will be delayed, but the host device can abort the dialogue.<ref name="SDHCspec"/>

Through issuing various commands, the host device can:<ref name="SDHCspec"/>
* Determine the type, memory capacity and capabilities of the SD card
* Command the card to use a different voltage, different clock speed, or advanced electrical interface
* Prepare the card to receive a block to write to the flash memory, or read and reply with the contents of a specified block.

The command interface is an extension of the [[MultiMediaCard]] (MMC) interface. SD cards dropped support for some of the commands in the MMC protocol, but added commands related to copy protection. By using only commands supported by both standards until determining the type of card inserted, a host device can accommodate both SD and MMC cards.

====Electrical interface====
All SD card families initially use a 3.3&nbsp;[[volt]] electrical interface. On command, SDHC and SDXC cards can switch to 1.8&nbsp;V operation.<ref name="SDHCspec"/>

At power-up or card insertion, the voltage on pin 1 selects either the Serial Peripheral Interface (SPI) bus or the SD bus. The SD bus starts in one-bit mode, but the host device may issue a command to switch to the four-bit mode, if the SD card supports it. For various card types, support for the four-bit SD bus is either optional or mandatory.<ref name="SDHCspec"/>

After determining that the SD card supports it, the host device can also command the SD card to switch to a [[#Speed|higher transfer speed]]. Until determining the card's capabilities, the host device should not use a clock speed faster than 400&nbsp;kHz. SD cards other than SDIO (see below) have a "Default Speed" clock rate of 25&nbsp;MHz. The host device is not required to use the maximum clock speed that the card supports. It may operate at less than the maximum clock speed to conserve power.<ref name="SDHCspec"/> Between commands, the host device can stop the clock entirely.

====MBR and FAT====
{{More citations needed|section|date=September 2023}}
Most SD cards ship preformatted with one or more [[Master boot record|MBR partitions]], where the first or only partition contains a [[file system]]. This lets them operate like the [[hard disk]] of a [[personal computer]]. Per the SD card specification, an SD card is formatted with MBR and the following file system:

* For SDSC cards:
** Capacity of less than 32,680 logical sectors<!-- This is the exact condition as per the SD card spec. For operating systems to properly recognize this as FAT12, the cluster values used on the resulting volume must not be outside the range 002h..FF5h, a condition normally (but not necessarily) met implicitly when applying standard logical geometries on a FAT filesystem with less than 32680 logical sectors. We mention the logical sector count rather than the allowed cluster range here as this article is about SD cards specifically. --> (smaller than 16&nbsp;MB{{efn|name="here, MB = 1024"|reference=here, MB = 1024<sup>2</sup> B}}): [[FAT12]] with partition type [[Partition type#PID 01h|01h]] and [[BPB 3.0]] or [[EBPB 4.1]]<ref name="SDG_2000_SD-P2-V1.0">{{cite book
|title=SD Memory Card Specifications – PART 2 FILE SYSTEM SPECIFICATION – Version 1.0
|author=<!-- Staff writer(s); no by-line -->
|publisher=SD Group, Matsushita Electric Industrial Co., Ltd. (MEI), SanDisk Corporation, Toshiba Corporation
|date=February 2000
|version=1.0}}</ref>
** Capacity of 32,680 to 65,535 logical sectors (between 16&nbsp;MB and 32&nbsp;MB):{{efn|name="here, MB = 1024"}} [[FAT16]] with partition type [[Partition type#PID 04h|04h]] and [[BPB 3.0]] or [[EBPB 4.1]]<ref name="SDG_2000_SD-P2-V1.0"/>
** Capacity of at least 65,536 logical sectors (larger than 32&nbsp;MB):{{efn|name="here, MB = 1024"}} [[FAT16B]] with partition type [[Partition type#PID 06h|06h]] and [[EBPB 4.1]]<ref name="SDG_2000_SD-P2-V1.0"/>
* For SDHC cards:
** Capacity of less than 16,450,560<!-- CHS: 0..1023 / 0..254 (but not 255!) / 1 (but not 0!)..63 -> limit: 1024x255x63 = 16450560 --> logical sectors (smaller than 7.8&nbsp;GB): [[FAT32]] with partition type [[Partition type#PID 0Bh|0Bh]] and [[EBPB 7.1]]
** Capacity of at least 16,450,560 logical sectors (larger than 7.8&nbsp;GB): [[FAT32]] with partition type [[Partition type#PID 0Ch|0Ch]] and [[EBPB 7.1]]
* For SDXC cards: [[exFAT]] with partition type [[Partition type#PID 07h|07h]]

Most consumer products that take an SD card expect that it is partitioned and formatted in this way. Universal support for FAT12, FAT16, FAT16B and FAT32 allows the use of SDSC and SDHC cards on most host computers with a compatible SD reader, to present the user with the familiar method of named files in a hierarchical directory tree.{{citation needed|date=September 2023}}

On such SD cards, standard utility programs such as Mac OS X's "{{Nowrap|[[Disk Utility]]}}" or Windows' [[SCANDISK]] can be used to repair a corrupted filing system and sometimes recover deleted files. [[Defragmentation]] tools for FAT file systems may be used on such cards. The resulting consolidation of files may provide a marginal improvement in the time required to read or write the file,<ref name="Fragmentation_and_Speed">{{Citation | url = https://www.sdcard.org/developers/overview/speed_class/ | title = Fragmentation and Speed | date = 11 December 2020 | publisher = SD Card | access-date = 21 November 2011 | archive-date = 3 June 2018 | archive-url = https://web.archive.org/web/20180603051813/https://www.sdcard.org/developers/overview/speed_class/ | url-status = live }}</ref> but not an improvement comparable to defragmentation of hard drives, where storing a file in multiple fragments requires additional physical and relatively slow, movement of a drive head.{{citation needed|date=September 2023}} Moreover, defragmentation performs writes to the SD card that count against the card's rated lifespan. The write endurance of the physical memory is discussed in the article on [[Flash memory degradation|flash memory]]; newer technology to increase the storage capacity of a card provides worse write endurance.{{citation needed|date=September 2023}}

When reformatting an SD card with a capacity of at least 32&nbsp;MB{{efn|name="here, MB = 1024"}} (65,536 logical sectors or more), but not more than 2&nbsp;GB,{{efn|name="GiB"}} [[FAT16B]] with partition type [[Partition type#PID 06h|06h]] and [[EBPB 4.1]]<ref name="SDG_2000_SD-P2-V1.0"/> is recommended if the card is for a consumer device. (FAT16B is also an option for 4&nbsp;GB cards, but it requires the use of 64&nbsp;KB [[cluster (file system)|clusters]], which are not widely supported.) FAT16B does not support cards above 4&nbsp;GB{{efn|name="GiB"}} at all.

The SDXC specification mandates the use of [[Microsoft]]'s [[proprietary format|proprietary]] [[exFAT]] file system,<ref name="engadget_sdxc_2t_300m">{{cite web | url = https://www.engadget.com/2009/01/07/sdxc-memory-cards-promise-2tb-of-storage-300mbps-transfer/ | title = SDXC memory cards promise 2 TB of storage, 300 MBps transfer | publisher = Engadget | date = 2009-01-07 | access-date = 2010-08-22 | archive-date = 2010-02-11 | archive-url = https://web.archive.org/web/20100211152502/http://www.engadget.com/2009/01/07/sdxc-memory-cards-promise-2tb-of-storage-300mbps-transfer | url-status = live }}</ref> which sometimes requires appropriate drivers (e.g. <code>exfat-utils</code>/<code>exfat-fuse</code> on Linux).

====Risks of reformatting====
Reformatting an SD card with a different file system, or even with the same one, may make the card slower, or shorten its lifespan. Some cards use [[wear leveling]], in which frequently modified blocks are mapped to different portions of memory at different times, and some wear-leveling algorithms are designed for the access patterns typical of FAT12, FAT16 or FAT32.<ref>{{cite web |url=https://lwn.net/Articles/428584/ |title=Optimizing Linux with cheap flash drives |publisher=Linux Weekly News |access-date=2011-04-11 |archive-date=2013-10-07 |archive-url=https://web.archive.org/web/20131007144837/http://lwn.net/Articles/428584/ |url-status=live }}</ref> In addition, the preformatted file system may use a cluster size that matches the erase region of the physical memory on the card; reformatting may change the cluster size and make writes less efficient. The SD Association provides freely downloadable SD Formatter software to overcome these problems for Windows and Mac OS X.<ref name=sdfmt>[https://www.sdcard.org/downloads/formatter/ SD Formatter 3.1 for SD/SDHC/SDXC] {{Webarchive|url=https://web.archive.org/web/20210207122439/https://www.sdcard.org/downloads/formatter/ |date=2021-02-07 }}, SD Association</ref>

SD/SDHC/SDXC memory cards have a "Protected Area" on the card for the SD standard's security function. Neither standard formatters nor the SD Association formatter will erase it. The SD Association suggests that devices or software which use the SD security function may format it.<ref name=sdfmt/>

===Power consumption===
The power consumption of SD cards varies by its speed mode, manufacturer and model.{{citation needed|date=September 2023}}

During transfer it may be in the range of 66–330&nbsp;mW (20–100&nbsp;mA at a supply voltage of 3.3&nbsp;V). Specifications from [[TwinMOS|TwinMOS Technologies]] list a maximum of 149&nbsp;mW (45&nbsp;mA) during transfer. Toshiba lists 264–330&nbsp;mW (80–100&nbsp;mA).<ref>{{Citation | url = http://www.toshiba-memory.com/en/micro_sd_cards.html | contribution = microSD & microSDHC Cards | publisher = Toshiba | title = Memory Solutions | access-date = 2011-02-27 | archive-date = 2013-08-18 | archive-url = https://web.archive.org/web/20130818222944/http://www.toshiba-memory.com/en/micro_sd_cards.html | url-status = dead }}</ref> Standby current is much lower, less than 0.2&nbsp;mA for one 2006 microSD card.<ref>{{Citation | url = http://www.dtt8.com/images/micro-sd%20specification.pdf | publisher = DTT | title = Micro SD specification | url-status = dead | archive-url = https://web.archive.org/web/20130207004550/http://www.dtt8.com/images/micro-sd%20specification.pdf | archive-date = 2013-02-07 }}</ref> If there is data transfer for significant periods, battery life may be reduced noticeably; for reference, the capacity of smartphone batteries is typically around 6&nbsp;Wh (Samsung Galaxy S2: 1650&nbsp;mAh @ 3.7&nbsp;V).

Modern UHS-II cards can consume up to 2.88&nbsp;W, if the host device supports bus speed mode SDR104 or UHS-II. Minimum power consumption in the case of a UHS-II host is 720&nbsp;mW.{{citation needed|date=September 2023}}

{| class="wikitable" style="text-align:center"
|+ Card requirements in different bus speed modes<ref>{{Citation | url = https://docs.google.com/viewer?url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf | contribution = SD Specifications Version 4.10 | publisher = SD Association | title = 3.10.5 – Summary of Bus Speed Mode for UHS-II Card | access-date = 2013-09-01 | archive-date = 2013-10-29 | archive-url = https://web.archive.org/web/20131029011727/https://docs.google.com/viewer?url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf | url-status = live }}</ref>
|-
! Bus speed<br />mode !! Max. bus<br />speed<br />[MB/s] !! Max. clock<br />frequency<br />[MHz] !! Signal<br />voltage<br />[V] !! SDSC<br />[W] !! SDHC<br />[W] !! SDXC<br />[W]
|-
| HD312 || 312 || 52 || 0.4 || – || 2.88 || 2.88
|-
| FD156 || 156 || 52 || 0.4 || – || 2.88 || 2.88
|-
| SDR104 || 104 || 208 || 1.8 || – || 2.88 || 2.88
|-
| SDR50 || 50 || 100 || 1.8 || – || 1.44 || 1.44
|-
| DDR50 || 50 || 50 || 1.8 || – || 1.44 || 1.44
|-
| SDR25 || 25 || 50 || 1.8 || – || 0.72 || 0.72
|-
| SDR12 || 12.5 || 25 || 1.8 || – || 0.36 || 0.36 / 0.54
|-
| High Speed || 25 || 50 || 3.3 || 0.72 || 0.72 || 0.72
|-
| Default Speed || 12.5 || 25 || 3.3 || 0.33 || 0.36 || 0.36 / 0.54
|}

==Storage capacity and compatibilities==
All SD cards let the host device determine how much information the card can hold, and the specification of each SD family gives the host device a guarantee of the maximum capacity a compliant card reports.

By the time the version 2.0 (SDHC) specification was completed in June 2006,<ref>{{Citation | url = http://www.dramexchange.com/WeeklyResearch/Post/1/492.aspx | title = A look into how SDHC will affect the future Nand Flash market | newspaper = DRAMeXchange | date = December 2006 | access-date = 2007-03-08 | archive-date = 2008-02-04 | archive-url = https://web.archive.org/web/20080204235806/http://www.dramexchange.com/WeeklyResearch/Post/1/492.aspx | url-status = dead }}</ref> vendors had already devised 2&nbsp;GB and 4&nbsp;GB SD cards, either as specified in Version 1.01, or by creatively reading Version 1.00. The resulting cards do not work correctly in some host devices.<ref>{{Citation | url = http://www.hjreggel.net/cardspeed/special-sd.html | contribution = SD Compatibility | title = Card speed – Card Readers and Memory Cards | date = December 1, 2006 | publisher = HJ Reggel | access-date = January 31, 2007 | archive-date = January 25, 2007 | archive-url = https://web.archive.org/web/20070125090359/http://www.hjreggel.net/cardspeed/special-sd.html | url-status = live }}</ref><ref>{{cite web |url=http://www.eggheadcafe.com/software/aspnet/33338344/winxp-sp3-cant-read-4gb.aspx |title=WinXP SP3 cannot read 4GB SD card in multicard reader |publisher=Egg head cafe |access-date=2010-08-22 |archive-date=2012-07-30 |archive-url=https://archive.today/20120730165858/http://www.eggheadcafe.com/software/aspnet/33338344/winxp-sp3-cant-read-4gb.aspx |url-status=dead }}</ref>

===SDSC cards above 1&nbsp;GB===
[[File:Sd4gy crop.jpg|thumb|4&nbsp;GB SDSC card]]

SD version 1.00 assumed 512 bytes per block. This permitted SDSC cards up to 4,096 × 512 × 512 B = 1&nbsp;GB.{{efn|name="GiB"}}

Version 1.01 let an SDSC card use a 4-bit field to indicate 1,024 or 2,048 bytes per block instead.<ref name="SDHCspec"/> Doing so enabled cards with 2&nbsp;GB and 4&nbsp;GB capacity, such as the Transcend 4&nbsp;GB SD card, the Memorette 4&nbsp;GB SD card and the Hoco 4&nbsp;GB microSD card.{{citation needed|date=September 2023}}

===Storage capacity calculations===
The format of the Card-Specific Data (CSD) register changed between version 1 (SDSC) and version 2.0 (which defines SDHC and SDXC).

====Version 1====
In version 1 of the SD specification, capacities up to 2&nbsp;GB{{efn|name="GiB"}} are calculated by combining fields of the CSD as follows:

 Capacity = ('''C_SIZE''' + 1) × 2<sup>('''C_SIZE_MULT''' + '''READ_BL_LEN''' + 2)</sup>
 where
  0 ≤ '''C_SIZE''' ≤ 4095,
  0 ≤ '''C_SIZE_MULT''' ≤ 7,
  '''READ_BL_LEN''' is 9 (for 512 bytes/sector) or 10 (for 1024 bytes/sector)

Later versions state (at Section 4.3.2) that a 2&nbsp;GB SDSC card shall set its READ_BL_LEN (and WRITE_BL_LEN) to indicate 1,024 bytes, so that the above computation correctly reports the card's capacity, but that, for consistency, the host device shall not request (by CMD16) block lengths over 512&nbsp;B.<ref name="SDHCspec"/>

====Versions 2 and 3====
{{More citations needed|section|date=September 2023}}

In the definition of SDHC cards in version 2.0, the C_SIZE portion of the CSD is 22 bits and it indicates the memory size in multiples of 512&nbsp;KB (the C_SIZE_MULT field is removed and READ_BL_LEN is no longer used to compute capacity). Two bits that were formerly reserved now identify the card family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved.<ref name="SDHCspec"/> Because of these redefinitions, older host devices do not correctly identify SDHC or SDXC cards nor their correct capacity.

* SDHC cards are restricted to reporting a capacity not over 32&nbsp;GB.{{citation needed|date=September 2023}}
* SDXC cards are allowed to use all 22 bits of the C_SIZE field. An SDHC card that did so (reported C_SIZE > 65,375 to indicate a capacity of over 32&nbsp;GB) would violate the specification. A host device that relied on C_SIZE rather than the specification to determine the card's maximum capacity might support such a card, but the card might fail in other SDHC-compatible host devices.{{citation needed|date=September 2023}}

Capacity is calculated thus:

 Capacity = ('''C_SIZE''' + 1) × 524288
 where for SDHC
  4112 ≤ '''C_SIZE''' ≤ 65375
  ≈2&nbsp;GB ≤ Capacity ≤ ≈32&nbsp;GB
 where for SDXC
  65535 ≤ '''C_SIZE'''
  ≈32&nbsp;GB ≤ Capacity ≤ 2&nbsp;TB{{citation needed|date=September 2023}}

Capacities above 4&nbsp;GB can only be achieved by following version 2.0 or later versions. In addition, capacities equal to 4&nbsp;GB must also do so to guarantee compatibility.{{citation needed|date=September 2023}}

==Openness of specification==
{{More citations needed|section|date=September 2023}}
[[File:MicroSD to SD adapter, disassembled.png|thumb|Dismantled microSD to SD adapter showing the passive connection from the microSD card slot on the bottom to the SD pins on the top]]
Like most memory card formats, SD is covered by numerous [[patent]]s and [[trademark]]s. Excluding [[Secure Digital#SDIO cards|SDIO]] cards, [[Royalty payment|royalties]] for SD card licenses are imposed for manufacture and sale of memory cards and host adapters (US$1,000/year plus membership at US$1,500/year){{citation needed|date=September 2023}}

Early versions of the SD specification were available under a [[non-disclosure agreement]] (NDA) prohibiting development of [[open-source software|open-source]] drivers. However, the system was eventually [[reverse-engineered]] and free software drivers provided access to SD cards not using DRM. Subsequent to the release of most open-source drivers, the SDA provided a simplified version of the specification under a less restrictive license helping reduce some incompatibility issues.<ref>{{cite web |url=http://www.linux.com/archive/feed/20060 |title=Sharp Linux PDA promotes the use of proprietary SD card, but more open MMC works just fine |date=14 June 2007 |publisher=Linux.com |access-date=2010-08-22 |archive-date=2010-12-15 |archive-url=https://web.archive.org/web/20101215172756/http://www.linux.com/archive/feed/20060 |url-status=live }}</ref>

Under a disclaimers agreement, the simplified specification released by the SDA in 2006 – as opposed to that of SD cards – was later extended to the physical layer, ASSD extensions, SDIO and SDIO [[Bluetooth]] Type-A.<ref>[http://www.sdcard.org/developers/tech/sdcard/pls/ Simplified Specification Agreement] {{webarchive |url=https://web.archive.org/web/20081028165644/http://www.sdcard.org/developers/tech/sdcard/pls/ |date=2008-10-28}} from the SDA's website</ref>

The Simplified Specification<ref>{{Cite web |url=https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |title=Simplified Specification|accessdate=July 31, 2024 |archive-date=December 18, 2020|archive-url=https://web.archive.org/web/20201218104400/https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |url-status=live}}</ref> is available.

Again, most of the information had already been discovered and [[Linux]] had a fully free driver for it. Still, building a chip conforming to this specification caused the [[One Laptop per Child]] project to claim "the first truly Open Source SD implementation, with no need to obtain an SDI license or sign NDAs to create SD drivers or applications."<ref>{{cite web|url=http://mailman.laptop.org/pipermail/community-news/2006-September/000023.html |title=OLPC mailing list archive |publisher=Mailman.laptop.org |access-date=2010-08-22 |archive-url=https://web.archive.org/web/20110412094819/http://mailman.laptop.org/pipermail/community-news/2006-September/000023.html |archive-date=2011-04-12}}</ref>

The proprietary nature of the complete SD specification affects [[embedded system]]s, laptop computers and some desktop computers; many desktop computers do not have card slots, instead using [[USB]]-based [[card reader#Memory card readers|card readers]] if necessary.{{citation needed|date=September 2023}} These card readers present a standard [[USB mass storage]] interface to memory cards, thus separating the operating system from the details of the underlying SD interface.{{citation needed|date=September 2023}} However, embedded systems (such as portable music players) usually gain direct access to SD cards and thus need complete programming information.{{citation needed|date=September 2023}} Desktop card readers are themselves embedded systems; their manufacturers have usually paid the SDA for complete access to the SD specifications.{{citation needed|date=September 2023}} Many notebook computers now include SD card readers not based on USB; device drivers for these essentially gain direct access to the SD card, as do embedded systems.{{citation needed|date=September 2023}}

The [[Serial Peripheral Interface Bus|SPI]]-bus interface mode is the only type that does not require a host license for accessing SD cards.{{citation needed|date=September 2023}}

[[File:Flash memory cards size.jpg|thumb|Size comparison of various flash cards: SD, [[CompactFlash]], [[MultiMediaCard|MMC]], [[xD-Picture Card|xD]]]]

==Data recovery==
A malfunctioning SD card can be repaired using specialized equipment, as long as the middle part, containing the flash storage, is not physically damaged. The controller can in this way be circumvented. This might be harder or even impossible in the case of monolithic card, where the controller resides on the same physical die.<ref>{{Cite web|url=https://blog.acelaboratory.com/pc-3000-flash-circuit-board-and-msd-card-preparing-and-soldering.html|title=PC-3000 Flash. How to recover data from a monolith (microSD card)|first=ACELab|last=team|access-date=2019-10-13|archive-date=2019-10-13|archive-url=https://web.archive.org/web/20191013042822/https://blog.acelaboratory.com/pc-3000-flash-circuit-board-and-msd-card-preparing-and-soldering.html|url-status=live}}</ref><ref>{{Cite web|url=https://rusolut.com/monolith-adapters/|title=New adapters for monolithic devices!|date=September 21, 2017|access-date=September 11, 2024|archive-date=February 4, 2018|archive-url=https://web.archive.org/web/20180204070430/https://rusolut.com/monolith-adapters/|url-status=live}}</ref>

==See also==
* [[Comparison of memory cards]]
* [[Microdrive]]
* [[Universal Flash Storage]]

==Footnotes==
{{notelist}}

==References==
{{Reflist}}

==External links==
{{Commons category multi|Secure Digital|miniSD|microSD}}
* [https://www.sdcard.org/ SD Association Official Site]
** [https://www.sdcard.org/downloads/pls/ SD simplified specifications]
** [https://www.sdcard.org/downloads/formatter/ SD Memory Card Formatter]
* [https://web.archive.org/web/20210812130158/http://elm-chan.org/docs/mmc/mmc_e.html How to Use MMC/SDC] elm-chan.org, December 26, 2019
* [https://web.archive.org/web/20210401202138/http://lwn.net/Articles/428584/ Optimizing Linux with cheap flash drives] [[lwn.net]]
* [https://web.archive.org/web/20171016194250/https://wiki.linaro.org/WorkingGroups/KernelArchived/Projects/FlashCardSurvey Flash memory card: design, and List of cards and their characteristics] [[linaro]]
* [https://havecamerawilltravel.com/fastest-sd-cards/ Independent SD Card Speed Tests]
** [https://havecamerawilltravel.com/sd-cards-explained/ Types of Memory Cards and Sizes]

{{Memory Cards}}
{{Authority control}}

[[Category:Computer-related introductions in 1999]]
[[Category:Japanese inventions]]
[[Category:Solid-state computer storage media]]