SD card#SDIO, SDHC, and SDXC

In 1999, SanDisk, Panasonic (Matsushita) and Toshiba agreed to develop and market the Secure Digital (SD) memory card.{{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}}{{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}} The card was created as a second-generation successor to the MultiMediaCard (MMC){{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}} 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.{{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}}

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.{{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}}

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{{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 }} became available in the first quarter of 2000, and production quantities of 32 and 64 megabyte (MB){{efn|except where indicated otherwise, 1 MB equals one million bytes}} cards became available three months later.{{citation needed|date=September 2023}} The first 64 MB cards were offered for sale for US$200.{{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}} 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.{{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}} The first 256 MB and 512 MB SD cards were announced in 2001.{{cite web | url=https://m.dpreview.com/articles/9501387485/sdmmc256mb512mb | title=256 and 512 MB MMC / SD cards }}

File:MiniSD memory card including adapter.jpg

At March 2003 CeBIT, SanDisk Corporation introduced, announced and demonstrated the miniSD form factor.[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 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}}

File:Samsung Galaxy A02s microSD slot.JPG]]

MicroSD form-factor memory cards were introduced in 2004 by SanDisk at CeBIT{{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}} and originally called T-Flash,{{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 }} and later TransFlash,{{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}} commonly abbreviated to "TF". T-Flash was renamed microSD in 2005 when it was adopted by the SDA.

{{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 }}

TransFlash and microSD cards are functionally identical, allowing either to operate in devices made for the other.{{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 }} A passive adapter allows the use of microSD and TransFlash cards in SD card slots.{{Cite web|url=https://ko.com.ua/cebit_2004_nastraivaemsya_na_volnu_budushhego_16835|title=CeBIT 2004: "Настраиваемся на волну будущего" | Статьи | 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}}

File:8 bytes vs. 8Gbytes.jpg (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 GB miniSDHC.[http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=3530 SanDisk Introduces 4 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 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}}

File:MicroSDXC.64GB.P1127589.jpg

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 gigabytes.

In January 2009, the SDA announced the SDXC family, which supports cards up to 2 TB{{efn|name="here, 1 TB = 1024"|reference=here, 1 TB = 1024⁴ B}} and speeds up to 300 MB/s.{{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 }} SDXC cards are formatted with the exFAT file system by default.{{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}} 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 TB{{efn|name="here, 1 TB = 1024"}} maximum as SDXC,{{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}} and Panasonic announced plans to produce 64 GB SDXC cards.{{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}} On March 6, Pretec introduced the first SDXC card,{{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}} a 32 GB card with a read/write speed of 400 Mbit/s. But only early in 2010 did compatible host devices come onto the market, including Sony's Handycam HDR-CX55V camcorder, Canon's EOS 550D (also known as Rebel T2i) Digital SLR camera,{{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}} a USB card reader from Panasonic, and an integrated SDXC card reader from 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}} 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.{{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}}

In early 2010, commercial SDXC cards appeared from Toshiba (64 GB),{{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}}{{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 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}} Panasonic (64 GB and 48 GB),{{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 GB* and 48 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}} and SanDisk (64 GB).{{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}}

In early 2011, Centon Electronics, Inc. (64 GB and 128 GB) and Lexar (128 GB) began shipping SDXC cards rated at Speed Class 10.{{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}} Pretec offered cards from 8 GB to 128 GB rated at Speed Class 16.{{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}} In September 2011, SanDisk released a 64 GB microSDXC card.{{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}} Kingmax released a comparable product in 2011.{{Citation |url=https://www.engadget.com/2011/05/26/kingmax-flaunts-worlds-first-64gb-microsd-card/ |title=Kingmax flaunts world's first 64 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}}

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.{{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}}{{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}} An adapter allows MicroP2 cards to work in current P2 card equipment.{{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}}

Panasonic MicroP2 cards shipped in March 2013 and were the first UHS-II compliant products on market; initial offer includes a 32 GB SDHC card and a 64 GB SDXC card.{{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}} Later that year, Lexar released the first 256 GB SDXC card, based on 20 nm NAND flash technology.{{cite web|title=Lexar Announces Industry's First 256 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}}

In February 2014, SanDisk introduced the first 128 GB microSDXC card,{{cite web|url=http://www.sandisk.com/about-sandisk/press-room/press-releases/2014/sandisk-introduces-worlds-highest-capacity-microsdxc-memory-card-at-128 gb/|title=SANDISK INTRODUCES WORLD'S HIGHEST CAPACITY microSDXC MEMORY CARD AT 128GB|last=SanDisk|website=sandisk.com}} which was followed by a 200 GB microSDXC card in March 2015.{{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}} September 2014 saw SanDisk announce the first 512 GB SDXC card.{{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}}

Samsung announced the world's first EVO Plus 256 GB microSDXC card in May 2016,{{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}} and in September 2016 Western Digital (SanDisk) announced that a prototype of the first 1 TB{{efn|reference=except where stated otherwise, in this article 1 TB = 1000 billion bytes}} SDXC card would be demonstrated at Photokina.{{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}}

In August 2017, SanDisk launched a 400 GB microSDXC card.{{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}}

In January 2018, Integral Memory unveiled its 512 GB microSDXC card.{{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}} In May 2018, PNY launched a 512 GB microSDXC card. In June 2018 Kingston announced its Canvas series of microSD cards which were capable of capacities up to 512 GB,{{efn|name="GiB"|reference=here, 1 GB = 1 GiB = 2³⁰ B}} in three variations, Select, Go! and React.{{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}}

In February 2019, Micron and SanDisk unveiled their microSDXC cards of 1 TB capacity.{{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}}

In September 2022, Kioxia unveiled a microSDXC card of 2 TB capacity.{{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 }}

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

In April 2024, Western Digital (SanDisk) revealed the world's first 4 TB SD card at NAB 2024, which will make use of the SDUC format. It is set to release in 2025.{{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}}

Secure Digital includes five card families available in three form factors. The five families are the original standard capacity (SDSC), high capacity (SDHC), extended capacity (SDXC), ultra capacity (SDUC) and SDIO, which combines input/output functions with data storage.{{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}}{{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}}{{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}}

{{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}}{{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}} thick, with microSD versions being {{Convert|1.0|mm|abbr=in}} 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 mm,{{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}} 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 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.{{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 }}{{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 }}
• 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}}

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 GB.{{efn|name="GiB"}} The SDHC trademark is licensed to ensure compatibility.[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}}

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 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 MB/s.[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.

SDHC host devices are required to accept older SD cards.[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. However, older host devices do not recognize SDHC or SDXC memory cards, although some devices can do so through a firmware upgrade.[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.{{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.{{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 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}}{{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}}{{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}}

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 TB,{{efn|name="here, 1 TB = 1024"}} compared to a limit of 32 GB{{efn|name="GiB"}} for SDHC cards in the SD 2.0 specification. SDXC adopts Microsoft's exFAT file system as a mandatory feature.{{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}}

Version 3.01 also introduced the Ultra High Speed (UHS) bus for both SDHC and SDXC cards, with interface speeds from 50 MB/s to 104 MB/s for four-bit UHS-I bus.{{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}} (this number has since been exceeded with SanDisk proprietary technology for 170 MB/s read, which is not proprietary anymore, as Lexar has the 1066x running at 160 MB/s read and 120 MB/s write via UHS 1, and Kingston also has their Canvas Go! Plus, also running at 170 MB/s).{{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}}{{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}}{{Cite web |title=Canvas Go! Plus Class 10 SD Cards – UHS-I, U3, V30 – 64 GB–512 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}}{{Cite web |title=Canvas Go! Plus Class 10 microSD Cards – V30, A2 – 64 GB–512 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}}

Version 4.0, introduced in June 2011, allows speeds of 156 MB/s to 312 MB/s over the four-lane (two differential lanes) UHS-II bus, which requires an additional row of physical pins.

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.{{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}}{{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}} The new ratings define a minimal write speed of 90 MB/s.{{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}}{{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}}

SDXC cards are required to be formatted using exFAT, but many operating systems will support others.{{citation needed|date=October 2024}}

Windows Vista (SP1) and later{{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=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 }} and OS X (10.6.5 and later) have native support for exFAT.{{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 }}{{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 }} (Windows XP and Server 2003 can support exFAT via an optional update from Microsoft.){{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}}

Most 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.{{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 }} Users of older kernels or BSD can manually install third-party implementations of exFAT (as a FUSE module) in order to be able to mount exFAT-formatted volumes.{{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 }} However, SDXC cards can be reformatted to use any file system (such as ext4, 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.{{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 }}

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.{{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 }}{{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 }}{{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 }}

The Secure Digital Ultra Capacity (SDUC) format, described in the SD 7.0 specification, and announced in June 2018, supports cards up to 128 TB,{{efn|name="here, 1 TB = 1024"}} regardless of form factor, either micro or full size, or interface type including UHS-I, UHS-II, UHS-III or SD Express.{{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}}

SD card speed is customarily rated by its sequential read or write speed. The sequential performance aspect is the most relevant for storing and retrieving large files (relative to block sizes internal to the flash memory), such as images and multimedia. Small data (such as file names, sizes and timestamps) falls under the much lower speed limit of random access, which can be the limiting factor in some use cases.{{Citation | url = http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf | title = Revisiting Storage for Smartphones | first1 = H | last1 = Kim | first2 = N | last2 = Agrawal | first3 = C | last3 = Ungureanu | publisher = NEC Laboratories | place = America | at = table 3 | date = 2012-01-30 | 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. | access-date = 2012-12-27 | archive-date = 2012-10-10 | archive-url = https://web.archive.org/web/20121010194100/http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf | url-status = live }}{{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|access-date=29 November 2015|date=2014-01-16|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.|archive-date=2015-12-08|archive-url=https://web.archive.org/web/20151208112031/http://goughlui.com/2014/01/16/testing-sd-card-performance-round-up/|url-status=live}}{{cite web|url=http://www.raspberrypi.org/forums/viewtopic.php?t=4076|title=Raspberry Pi forum: SD card benchmarks|access-date=2014-08-12|archive-date=2014-08-13|archive-url=https://web.archive.org/web/20140813011920/http://www.raspberrypi.org/forums/viewtopic.php?t=4076|url-status=live}}

The newer families of SD card improve card speed by increasing the bus rate (the frequency of the clock signal that strobes information into and out of the card). Whatever the bus rate, the card can signal to the host that it is "busy" until a read or a write operation is complete. Compliance with a higher speed rating is a guarantee that the card limits its use of the "busy" indication.

SD cards will read and write at speeds of 12.5 MB/s.

High-Speed Mode (25 MB/s) was introduced to support digital cameras with 1.10 spec version.{{Cite web |url= https://www.sdcard.org/developers/overview/bus_speed/ |title= Bus Speed (Default Speed/High Speed/UHS/SD Express) |publisher= SD Association |website= SD card |access-date= 2020-04-18 |archive-date= 2016-10-04 |archive-url= https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |url-status= live }}

The Ultra High Speed (UHS) bus is available on some SDHC and SDXC cards.{{cite web |url= https://www.sdcard.org/developers/overview/bus_speed/ |title= Bus Speed (Default Speed/ High Speed/ UHS) |publisher= SD Association |work= SD card |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 }}{{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}}{{cite web |last=Rigg |first=Jamie |url=https://www.engadget.com/2013/07/16/toshiba-exceria-pro-sd-cards/ |title=Toshiba's Exceria Pro SDHC cards claim 'world's fastest' write speeds of 240 MB per second |work=Engadget |date=2013-07-16 |access-date=2014-01-02 |archive-date=2013-12-19 |archive-url=https://web.archive.org/web/20131219033502/http://www.engadget.com/2013/07/16/toshiba-exceria-pro-sd-cards/ |url-status=live }}

Cards that comply with UHS show Roman numerals 'I', 'II' or 'III' next to the SD card logo,{{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=SDCard.org}} and report this capability to the host device. Use of UHS-I requires that the host device command the card to drop from 3.3-volt to 1.8-volt operation over the I/O interface pins and select the four-bit transfer mode, while UHS-II requires 0.4-volt operation.

The higher speed rates of UHS-II and III are achieved by using two-lane 0.4 V low-voltage differential signaling (LVDS) on a second row of pins.{{cite web |title=SD Standard Overview |url=https://www.sdcard.org/developers/sd-standard-overview/ |website=SD Association |date=11 December 2020 |access-date=19 June 2023}} Each lane is capable of transferring up to 156 MB/s. In full-duplex mode, one lane is used for Transmit while the other is used for Receive. In half-duplex mode both lanes are used for the same direction of data transfer allowing a double data rate at the same clock speed. In addition to enabling higher data rates, the UHS-II interface allows for lower interface power consumption, lower I/O voltage and lower electromagnetic interference (EMI).

The following ultra-high speeds are specified:

Specified in SD version 3.01.{{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 }} Supports a clock frequency of 100 MHz (a quadrupling of the original "Default Speed"), which in four-bit transfer mode could transfer 50 MB/s (SDR50). UHS-I cards declared as UHS104 (SDR104) also support a clock frequency of 208 MHz, which could transfer 104 MB/s. Double data rate operation at 50 MHz (DDR50) is also specified in Version 3.01, and is mandatory for microSDHC and microSDXC cards labeled as UHS-I. In this mode, four bits are transferred when the clock signal rises and another four bits when it falls, transferring an entire byte on each full clock cycle, hence a 50 MB/s operation could be transferred using a 50 MHz clock.

There is a proprietary UHS-I extension, called DDR200, originally created by SanDisk that increases transfer speed further to 170 MB/s. Unlike UHS-II, it does not use additional pins. It achieves this by using the 208 MHz frequency of the standard SDR104 mode, but using DDR transfers.{{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 }}{{Cite web |website=Genesys Logic |title=GL3232 |url=http://www.genesyslogic.com/en/product_view.php?show=83 |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 }} This extension has since then been used by Lexar for their 1066x series (160 MB/s), Kingston Canvas Go Plus (170 MB/s) and the MyMemory PRO SD card (180 MB/s).

File:Lexar 1000x MicroSDHC UHS-II U3 Class 10 - Back.jpg

Specified in version 4.0, further raises the data transfer rate to a theoretical maximum of 156 MB/s (full-duplex) or 312 MB/s (half-duplex) using an additional row of pins for LVDS signalling{{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 }} (a total of 17 pins for full-size and 16 pins for micro-size cards). 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.{{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}}

Version 6.0, released in February 2017, added two new data rates to the standard. FD312 provides 312 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.{{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}}

File:SD Express Highest Speed Card Standard.jpg

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 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.{{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 }} In February 2019, the SD Association announced microSD Express,{{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}} along with new visual marks to help users identify compatible cards and hosts.{{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}}

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.{{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}}

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 MB/s using an additional row of contacts.{{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}} Revisions continued with version 9.0 in February 2022{{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}} and version 9.1 in October 2023,{{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}} further refining the standard.

Adoption has been gradual. In February 2024, Samsung announced it was sampling its first microSD Express cards,{{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 }} though commercial availability remained limited. Interest increased when Nintendo confirmed in April 2025 that the upcoming Switch 2 would only support microSD Express cards, without backwards compatibility for UHS-I cards.{{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}}

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.

Where speed classes overlap, manufacturers often display multiple symbols on the same card to indicate compatibility with different host devices and standards.

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

Ultra High Speed (UHS) speed class ratings—U1 and U3—specify minimum sustained write speeds of 10 and 30 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.{{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}}

Video speed class ratings—V6, V10, V30, V60, and V90—specify minimum sustained write speeds of 6, 10, 30, 60, and 90 MB/s, respectively.{{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}} These classes are represented by a stylized "V" followed by the number, were introduced to support high-resolution formats like 4K and 8K, and to align with the performance characteristics of MLC NAND flash memory.

SD Express speed class ratings—E150, E300, E450, and E600—specify minimum sustained write speeds of 150, 300, 450, and 600 MB/s, respectively. 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.

{{main|CD and DVD writing speed}}

Initially, some manufacturers used a "×" rating system based on the speed of a standard CD-ROM drive (150 kB/s or 1.23 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.{{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}}{{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}}

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. 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.

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.{{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 }}

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 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 MB/s."{{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}}

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.{{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}}{{cite patent |country=US |number=7827370 |status=patent}}

{{more citations needed|section|date=September 2023}}

File:SD card unlocked and locked.svg

File:Vorderseite Sony Tough SF-M64T SDUHSII011CORRklein.png

Most full-size SD cards have a "mechanical write protect switch" allowing the user to advise the host computer that the user wants the device to be treated as read-only. This does not protect the data on the card if the host is compromised: "It is the responsibility of the host to protect the card. The position [i.e., setting] of the write protect switch is unknown to the internal circuitry of the card."{{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}} Some host devices do not support write protection, which is an optional feature of the SD specification, and drivers and devices that do obey a read-only indication may give the user a way to override it.{{citation needed|date=September 2023}}

The switch is a sliding tab that covers a notch in the card. The miniSD and microSD formats do not directly support a write protection notch, but they can be inserted into full-size adapters which do.{{citation needed|date=September 2023}}

When looking at the SD card from the top, the right side (the side with the beveled corner) must be notched.{{citation needed|date=September 2023}}

On the left side, there may be a write-protection notch. If the notch is omitted, the card can be read and written. If the card is notched, it is read-only. If the card has a notch and a sliding tab which covers the notch, the user can slide the tab upward (toward the contacts) to declare the card read/write, or downward to declare it read-only.{{citation needed|date=September 2023}} The diagram to the right shows an orange sliding write-protect tab in both the unlocked and locked positions.{{citation needed|date=September 2023}}

Cards sold with content that must not be altered are permanently marked read-only by having a notch and no sliding tab.{{citation needed|date=September 2023}}

{{more citations needed|section=yes|date=September 2023}}

File:Sdadaptersandcards.jpg

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".{{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}} 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.{{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}}

A smartSD memory card is a microSD card with an internal "secure element" that allows the transfer of ISO 7816 Application Protocol Data Unit commands to, for example, JavaCard applets running on the internal secure element through the SD bus.{{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}}

Some of the earliest versions of microSD memory cards with secure elements were developed in 2009 by DeviceFidelity, Inc.,{{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}}{{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}} 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 in 2010.{{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}} 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.{{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}}{{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}}{{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}}

Various implementations of smartSD cards have been done for payment applications and secured authentication.{{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}}{{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}} In 2012 Good Technology partnered with DeviceFidelity to use microSD cards with secure elements for mobile identity and access control.{{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}}

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,{{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}}{{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}}{{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 | 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}} while others were part of innovative new direct-to-consumer neobank programs such as moneto, first launched in 2012.{{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}}{{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}}{{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}}{{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}}

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.{{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}} 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.{{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}}{{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}} This was the first time regular mobile phones could be used to open doors without need for electronic access keys.

{{multiple image

| SD cards with integrated Wi-Fi

| perrow = 2

| total_width = 390

| image1 = Eye-Fi Wifi Card.jpg

| caption1 = Eye-Fi Mobi 16 GB

| image2 = FlashAir 014 (15247275839) (cropped).jpg

| caption2 = Toshiba FlashAir 16 GB

| image3 = Pqi-air-card 開箱 (8536928274) (cropped).jpg

| caption3 = PQI air card 4 GB

| image4 = Transcend WiFi SD-Card.jpg

| caption4 = Transcend Wi-Fi 16 GB

}}

File:USB-SD-Cards.jpg]]

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, Transcend Wi-Fi, Toshiba FlashAir, Trek Flucard, PQI Air Card and LZeal ez Share.{{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}} Some models 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.{{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}} In 2011, SanDisk offered various collections of 1000 songs on a single slotMusic card for about $40,{{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}} 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.{{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=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}} 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 used color-coded cards by Kingmax, which later other brands (e.g., SanDisk, Kioxia) had been implemented 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.{{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}}

{{more citations needed|section=yes|date=September 2023}}

File:SDIO Vector.svg

File:HP PhotoSmart SDIO Kamera (cropped).jpg 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, modems, barcode readers, FM radio tuners, TV tuners, RFID readers, digital cameras 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 USB device classes and Bluetooth profiles.){{citation needed|date=September 2023}}

The 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 kHz for all communications, and the use of Pin 8 as "interrupt" to try to initiate dialogue with the host device.{{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}}

Host devices that comply with newer versions of the specification provide backward compatibility and accept older SD cards. 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, there are several factors that arise:

• A newer card may offer greater capacity than the host device can handle (over 4 GB for SDHC, over 32 GB for SDXC).
• A newer card may use a 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 bits) and 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.
• Some vendors produced SDSC cards above 1 GB before the SDA had standardized a method of doing so.

File:Micro-SD-Kartenleser der Nintendo Switch 20230405 HOF09182 RAW-Export.png]]

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 cameras, camcorders and video game consoles, tend to use full-sized cards. Devices in which small size is paramount, such as mobile phones, action cameras such as the GoPro Hero series, and camera drones, tend to use microSD cards.{{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 }}{{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}}

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 plans, memory cards in mobile devices provide location-independent and 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 bricked devices is 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 technical development of memory cards, users of existing mobile devices are able to expand their storage further and priceworthier with time.{{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 }}{{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 }}{{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 }}

Recent versions of major operating systems such as Windows Mobile and 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.{{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}}

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 TB.{{efn|name="here, 1 TB = 1024"}}{{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 }}

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 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 (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.

File:Samsung Pro 64gb micro-SDXC original and falsification front and back.jpg Pro 64 GB microSDXC original (left) and counterfeit (right): The counterfeit claims to have 64 GB in capacity, but only 8 GB (Class 4 speed) are usable: When trying to write more than 8 GB, data loss occurs. Also used for SanDisk 64 GB fakes.]]

File:Decapsulated microSD memory card lineup-genuine, questionable, and fake-counterfeit.jpg]]

Commonly found on the market are mislabeled or counterfeit Secure Digital cards that report a fake capacity or run slower than labeled.{{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 }}{{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 }}{{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 }} Software tools exist to check and detect counterfeit products,{{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}}{{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}}{{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 }} and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.[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

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. MD5), or trying to 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 0xFFs).

File:Pentax K10D with SanDiskSD card.jpg camera]]

Secure Digital memory cards can be used in Sony XDCAM EX camcorders with an adapter.{{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 }}

Although many personal computers 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{{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 }} 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 computers, memory cards in an integrated memory card reader offer an ergonomical benefit over USB flash drives, 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 computers with installed SD card readers have been able to boot in macOS from SD storage devices, when properly formatted to Mac OS Extended file format and the default partition table set to GUID Partition Table.{{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 }}

SD cards are increasing in usage and popularity among owners of vintage computers like Atari 8-bit computers. For example SIO2SD (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 GB of disk size (2019).{{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}}

File:Arduino Ethernet Shield (pre-production sample).jpg) 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.{{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}} However this standard was not adopted by the market while the MMC standard became the de facto standard for embedded systems. SanDisk provides such embedded memory components under the iNAND brand.{{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}}

While some modern microcontrollers integrate SDIO hardware which uses the faster proprietary four-bit SD bus mode, almost all modern microcontrollers at least have 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-TM router and wired to GPIO pins using DD-WRT's Linux kernel achieved only {{Nowrap|1.6 Mbit/s}} throughput).{{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 }}

Prerecorded microSDs have been used to commercialize music under the brands slotMusic and slotRadio by SanDisk and MQS by Astell & Kern.

{{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

}}

{{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.

File:MicroSD MemoryCard 002.jpg

• 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)

• miniSD, miniSDHC, miniSDIO
• {{Nowrap|{{cvt|21.5|x|20|x|1.4|mm|frac=64}}}}

The micro form factor is the smallest SD card format.{{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}}

• microSD, microSDHC, microSDXC, microSDUC
• {{Nowrap|{{cvt|15|x|11|x|1|mm|frac=64}}}}

{{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 microcontrollers. 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_SS (Ground) pins.{{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 }}

File:MMC-SD-miniSD-microSD-Color-Numbers-Names.gif, 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.]]

Notes:

1. Direction is relative to card. I = Input, O = Output.
2. PP = Push-Pull logic, OD = Open-Drain logic.
3. S = Power Supply, NC = Not Connected (or logical high).

File:Sd insides.png chip that holds the data (bottom) and SD controller (top)]]

File:SD-extreMEmory 2GB alt innen.jpg chips (top and middle), SD controller chip (bottom)]]

File:Pretec 16GB SDHC without cover 20090420.jpg

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.

Through issuing various commands, the host device can:

• 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.

All SD card families initially use a 3.3 volt electrical interface. On command, SDHC and SDXC cards can switch to 1.8 V operation.

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.

After determining that the SD card supports it, the host device can also command the SD card to switch to a higher transfer speed. Until determining the card's capabilities, the host device should not use a clock speed faster than 400 kHz. SD cards other than SDIO (see below) have a "Default Speed" clock rate of 25 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. Between commands, the host device can stop the clock entirely.

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

Most SD cards ship preformatted with one or more 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 (smaller than 16 MB{{efn|name="here, MB = 1024"|reference=here, MB = 1024² B}}): FAT12 with partition type 01h and BPB 3.0 or EBPB 4.1{{cite book

|title=SD Memory Card Specifications – PART 2 FILE SYSTEM SPECIFICATION – Version 1.0

|author=

|publisher=SD Group, Matsushita Electric Industrial Co., Ltd. (MEI), SanDisk Corporation, Toshiba Corporation

|date=February 2000

|version=1.0}}

• Capacity of 32,680 to 65,535 logical sectors (between 16 MB and 32 MB):{{efn|name="here, MB = 1024"}} FAT16 with partition type 04h and BPB 3.0 or EBPB 4.1
• Capacity of at least 65,536 logical sectors (larger than 32 MB):{{efn|name="here, MB = 1024"}} FAT16B with partition type 06h and EBPB 4.1
• For SDHC cards:
• Capacity of less than 16,450,560 logical sectors (smaller than 7.8 GB): FAT32 with partition type 0Bh and EBPB 7.1
• Capacity of at least 16,450,560 logical sectors (larger than 7.8 GB): FAT32 with partition type 0Ch and EBPB 7.1
• For SDXC cards: exFAT with partition type 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,{{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 }} 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; 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 MB{{efn|name="here, MB = 1024"}} (65,536 logical sectors or more), but not more than 2 GB,{{efn|name="GiB"}} FAT16B with partition type 06h and EBPB 4.1 is recommended if the card is for a consumer device. (FAT16B is also an option for 4 GB cards, but it requires the use of 64 KB clusters, which are not widely supported.) FAT16B does not support cards above 4 GB{{efn|name="GiB"}} at all.

The SDXC specification mandates the use of Microsoft's proprietary exFAT file system,{{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 }} which sometimes requires appropriate drivers (e.g. exfat-utils/exfat-fuse on Linux).

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.{{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 }} 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.[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

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.

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 mW (20–100 mA at a supply voltage of 3.3 V). Specifications from TwinMOS Technologies list a maximum of 149 mW (45 mA) during transfer. Toshiba lists 264–330 mW (80–100 mA).{{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 }} Standby current is much lower, less than 0.2 mA for one 2006 microSD card.{{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 }} 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 Wh (Samsung Galaxy S2: 1650 mAh @ 3.7 V).

Modern UHS-II cards can consume up to 2.88 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 mW.{{citation needed|date=September 2023}}

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,{{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 }} vendors had already devised 2 GB and 4 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.{{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 }}{{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 }}

File:Sd4gy crop.jpg

SD version 1.00 assumed 512 bytes per block. This permitted SDSC cards up to 4,096 × 512 × 512 B = 1 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. Doing so enabled cards with 2 GB and 4 GB capacity, such as the Transcend 4 GB SD card, the Memorette 4 GB SD card and the Hoco 4 GB microSD card.{{citation needed|date=September 2023}}

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

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

Capacity = (C_SIZE + 1) × 2^{(C_SIZE_MULT + READ_BL_LEN + 2)}

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 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 B.

{{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 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. 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 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 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 GB ≤ Capacity ≤ ≈32 GB

where for SDXC

65535 ≤ C_SIZE

≈32 GB ≤ Capacity ≤ 2 TB{{citation needed|date=September 2023}}

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

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

File:MicroSD to SD adapter, disassembled.png

Like most memory card formats, SD is covered by numerous patents and trademarks. Excluding SDIO cards, 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 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.{{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 }}

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.[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

The Simplified Specification{{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}} 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."{{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}}

The proprietary nature of the complete SD specification affects embedded systems, laptop computers and some desktop computers; many desktop computers do not have card slots, instead using USB-based 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 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, MMC, xD]]

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.{{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}}{{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}}

• Comparison of memory cards
• Microdrive
• Universal Flash Storage

{{notelist}}

{{Reflist}}

{{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