View source for SD card

{{Redirect|SDHC|the gene|SDHC (gene)}}
{{Short description|Flash memory card format}}
{{Use mdy dates|date=June 2025}}
{{Infobox storage medium
| name = SD card
| logo = [[File:SD-Logo.svg|frameless|upright=0.5|class=skin-invert]]
| image = SD Cards.svg{{!}}class=skin-invert
| caption = From top to bottom: SD, miniSD, microSD
| type = [[Memory card]]
| capacity = {{ubli
 | '''SD''': Up to {{Nowrap|2 GB}}
 | '''SDHC''': Up to {{Nowrap|32 GB}}
 | '''SDXC''': Up to {{Nowrap|2 TB}}
 | '''SDUC''': Up to {{Nowrap|128 TB}}
 }}
| blocksize = Variable
| read = {{ubli
 | '''Default''': 12.5&nbsp;MB/s
 | '''High-speed''': 25&nbsp;MB/s
 | '''UHS-I''': Up to 104&nbsp;MB/s
 | '''UHS-II''': Up to 312&nbsp;MB/s
 | '''UHS-III''': Up to 624&nbsp;MB/s
 | '''Express''': Up to 3,940&nbsp;MB/s
 }}
| owner = [[SD Association]]
| dimensions = {{Unbulleted list
  | '''Standard''':
  | {{cvt|32|*|24|*|2.1|mm}}
  | {{cvt|1612.8|mm3}}
  | '''Mini''':
  | {{cvt|21.5|*|20|*|1.4|mm}}
  | {{cvt|602|mm3}}
  | '''Micro''':
  | {{cvt|15|*|11|*|1|mm}}
  | {{cvt|165|mm3}}
  }}
| weight = {{Unbulleted list
 | '''Standard''': {{Nowrap|~2 [[Gram|g]]}}
 | '''Mini''': {{Nowrap|~0.8 g}}
 | '''Micro''': {{Nowrap|~0.25 g}}
 }}
| extended from = [[MultiMediaCard]]
| extended to =
| released = August 1999
| discontinued =
}}

The '''SD card'''<!-- SDA decided not to use "Secure Digital" for the meaning of "SD" many years ago. --> is a [[proprietary hardware|proprietary]], [[non-volatile memory|non-volatile]], [[flash memory]] card format developed by the [[SD Association]] (SDA). They come in three physical forms: the full-size SD, the smaller '''miniSD''' (now [[Obsolescence|obsolete]]), and the smallest, '''microSD'''. Owing to their compact form factor, SD cards have been widely adopted in a variety of portable consumer electronics, including [[digital camera]]s, [[camcorder]]s, [[video game console]]s, [[mobile phone]]s, [[action camera]]s, and [[Unmanned aerial vehicle|camera drones]].<ref name="FB" /><ref name="Engadget 2016" />

The format was introduced in August 1999 as '''Secure Digital''' by [[SanDisk]], [[Panasonic]] (then known as Matsushita), and [[Kioxia]] (then part of [[Toshiba]]). It was designed as a successor to the [[MultiMediaCard]] (MMC) format, introducing several enhancements including a [[digital rights management]] (DRM) feature, a more durable physical casing, and a mechanical write-protect switch. These improvements, combined with strong industry support, contributed to its widespread adoption.

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

== History ==

=== Origins and standardization ===
In 1994, [[SanDisk]] introduced the [[CompactFlash]] (CF) format, one of the first successful flash memory card types.<ref name="Shendar 2022">{{cite web |last=Shendar |first=Ronni |date=2022-09-29 |title=The Invention of the SD Card: When Tiny Storage Met Tech Giants |url=https://blog.westerndigital.com/invention-sd-card/ |access-date=2025-06-19 |website=[[Western Digital]]}}</ref> CF outpaced several competing early formats, including the [[Miniature Card]] and [[SmartMedia]]. However, the late 1990s saw a proliferation of proprietary formats such as [[Sony]]'s [[Memory Stick]] and the [[xD-Picture Card]] from Olympus and Fujifilm, resulting in a fragmented memory card market.<ref name="Shendar 2022" />

To address these challenges, SanDisk partnered with [[Siemens]] and [[Nokia]] in 1996 to develop a new postage stamp-sized memory card called the [[MultiMediaCard]] (MMC). While technically innovative, MMC adoption was slow, and even Nokia was slow to integrate support for it into its mobile devices.<ref name="Shendar 2022" />

In 1999, SanDisk was approached by [[Panasonic]] (then known as Matsushita) and [[Kioxia]] (then part of [[Toshiba]]) to develop a new format as a second-generation successor to MMC.<ref>{{Cite web |last=Andrews |first=Ben |date=2022-10-25 |title=Flash back: the history of the SD card, and why we think it deserves more love |url=https://www.digitalcameraworld.com/features/flash-back-the-history-of-the-sd-card-and-why-we-think-it-deserves-more-love |access-date=2024-06-19 |website=Digital Photography Review}}</ref> The goal was to create a portable, high-performance memory card with integrated security features and broader interoperability. Concerned about losing market share to Sony's proprietary Memory Stick, Toshiba and Panasonic saw the collaboration as an opportunity to establish an open, industry-backed standard.<ref name="Shendar 2022" /><ref name="DP Review 1999">{{cite web |date=1999-08-24 |title=Matsushita Electric, SanDisk and Toshiba Agree to Join Forces to Develop and Promote Next Generation Secure Memory Card |url=http://www.dpreview.com/articles/6861681955/newmemory |url-status=live |archive-url=https://web.archive.org/web/20190904031748/http://www.dpreview.com/articles/6861681955/newmemory |archive-date=2019-09-04 |access-date=2016-02-23 |publisher=DP Review}}</ref>

Panasonic and Toshiba, who had previously collaborated on the [[Super Density Disc]] (a [[DVD]] precursor), reused its stylized "SD" logo for the Secure Digital (SD) card format.<ref>{{cite video |url=https://www.youtube.com/watch?v=VeLvdE8lNW4 |title=The Odd History of the SD Logo |access-date=2025-06-19}}</ref> Anticipating the growth of MP3 players, they also advocated for [[digital rights management]] (DRM) support seeking to reassure content publishers wary of piracy.<ref name="Shendar 2022" /><ref>{{cite web |date=2003-07-17 |title=Press Releases 17 July 2003 |url=http://www.toshiba.co.jp/about/press/2003_07/pr1701.htm |url-status=live |archive-url=https://web.archive.org/web/20100908075309/http://www.toshiba.co.jp/about/press/2003_07/pr1701.htm |archive-date=2010-09-08 |access-date=2010-08-22 |publisher=Toshiba}}</ref> The DRM system adopted—[[Content Protection for Recordable Media]] (CPRM)—had been developed earlier in partnership with [[IBM]] and [[Intel]], and Intel and complied with the [[Secure Digital Music Initiative]] standard.<ref>{{Cite web |date=June 2007 |title=SanDisk SD Card Product Family |url=https://static6.arrow.com/aropdfconversion/862ccebb5146463a796b084dde67a0ce0c60f7dc/sd_family_product.pdf |website=SanDisk}}</ref> Although often cited as a factor in the format's broad industry support, CPRM was rarely implemented in practice.<ref>{{Cite web |title=Definition of CPRM |url=https://www.pcmag.com/encyclopedia/term/cprm |url-status=live |archive-url=https://web.archive.org/web/20250429025631/https://www.pcmag.com/encyclopedia/term/cprm |archive-date=29 April 2025 |access-date=2025-04-29 |website=PCMAG |language=en}}</ref><ref>{{Cite web |title=Copyright Protection for Digital Data (CPRM) |url=https://www.sdcard.org/consumers/about-sd-memory-card-choices/copyright-protection-for-digital-data-cprm/ |url-status=live |archive-url=https://web.archive.org/web/20250429025631/https://www.sdcard.org/consumers/about-sd-memory-card-choices/copyright-protection-for-digital-data-cprm/ |archive-date=29 April 2025 |access-date=2025-04-29 |website=SD Association |language=en-US}}</ref> SD cards also featured a mechanical write-protect switch, and early SD slots maintained backward compatibility with MMC cards.<ref>{{Cite web |date=1999-08-25 |title=Three Giants to develop new "Secure Memory Card" |url=https://www.dpreview.com/articles/6861681955/newmemory |access-date=2025-06-19 |website=Digital Photography Review}}</ref>In early 2000, the first commercial SD cards offering 8 [[megabyte]] (MB){{efn|except where indicated otherwise, 1&nbsp;MB equals one million bytes}} of storage were released,<ref>{{Cite web |last=Udinmwen |first=Efosa |date=2025-05-24 |title=SD memory cards just hit 25—cloud storage won't kill them, and here's why they're still irreplaceable |url=https://www.techradar.com/pro/the-humble-sd-card-turns-25-as-memory-card-capacity-grew-one-million-times-and-speeds-by-a-factor-of-300 |access-date=2025-06-19 |website=TechRadar |language=en}}</ref> with larger capacity versions following shortly after. By August 2000, 64&nbsp;MB cards were being sold for approximately {{US$|200|2000|link=yes|round=-0}}.<ref>{{cite magazine |date=2000-08-27 |editor-last=Kantra Kirschner |editor-first=Suzanne |title=Electronics – Memory Cards |url=https://books.google.com/books?id=xA5vzkW8IDsC&pg=PA40 |access-date=2025-06-19 |magazine=[[Popular Science]] |page=40}}</ref> According to SanDisk, consumer adoption was accelerated by Toshiba and Panasonic's commitment to launching compatible devices in parallel with the cards.<ref name="Shendar 2022" />

To support standardization and interoperability, SanDisk, Toshiba, and Panasonic announced the creation of the [[SD Association]] (SDA) at the January 2000 [[Consumer Electronics Show]] (CES). Headquartered in [[San Ramon, California]], the SDA initially included 30 member companies and has since grown to encompass around 800 organizations worldwide.<ref>{{cite web |title=About the SD Association |url=https://www.sdcard.org/about/ |access-date=2025-06-19}}</ref>

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

At the March 2003 [[CeBIT]] trade show, SanDisk introduced and demonstrated the miniSD card format.<ref>{{cite web |date=2003-03-13 |title=SanDisk Introduces The World's Smallest Removable Flash Card For Mobile Phones—The miniSD Card |url=http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=1536 |archiveurl=https://web.archive.org/web/20090114232017/http://www.sandisk.com/Corporate/PressRoom/PressReleases/PressRelease.aspx?ID=1536 |archivedate=2009-01-14 |publisher=SanDisk}}</ref> The SD Association (SDA) adopted miniSD later that year as a small-form-factor extension to the SD card standard, intended primarily for use in mobile phones. However, the format was largely phased out by 2008 following the introduction of the even smaller microSD card.<ref>{{cite news |last=Buchanan |first=Matt |date=2008-10-01 |title=Giz Explains: An Illustrated Guide to Every Stupid Memory Card You Need |url=https://gizmodo.com/giz-explains-an-illustrated-guide-to-every-stupid-memo-5057252 |access-date=2025-06-19 |language=en-US}}</ref>

The microSD format was introduced by SanDisk at CeBIT in 2004,<ref>{{cite web |date=2004-03-22 |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 |url=https://www.itmedia.co.jp/news/articles/0403/22/news002.html |archive-url=https://web.archive.org/web/20240911012959/https://www.itmedia.co.jp/news/articles/0403/22/news002.html |archive-date=2024-09-11 |access-date=2025-06-19 |website=ITmedia NEWS}}</ref> initially under the name T-Flash,<ref>{{cite news |last=Rojas |first=Peter |date=2004-03-02 |title=T-Flash: aka 'Yet Another Memory Card Format' |url=https://www.engadget.com/2004/03/02/t-flash-aka-yet-another-memory-card-format/ |archive-url=https://web.archive.org/web/20190502064324/https://www.engadget.com/2004/03/02/t-flash-aka-yet-another-memory-card-format/ |archive-date=2019-05-02 |access-date=2025-06-19 |publisher=Engadget}}</ref> later rebranded as TransFlash or TF. In 2005, the SDA adopted the format under the official name microSD,<ref>{{cite web |title=TransFlash becomes MicroSD |url=https://www.theregister.com/2005/07/14/transflash_is_microsd/ |archive-url=https://web.archive.org/web/20240911012959/https://www.theregister.com/2005/07/14/transflash_is_microsd/ |archive-date=2024-09-11 |access-date=2025-06-19}}</ref><ref>{{cite web |date=2004-02-28 |title=SanDisk Reveals Tiny New Memory Cards for Phones |url=https://www.phonescoop.com/articles/article.php?a=801 |archive-url=https://web.archive.org/web/20120722005048/http://www.phonescoop.com/articles/article.php?a=801 |archive-date=2012-07-22 |access-date=2025-06-19 |publisher=Phonescoop}}</ref> though the TransFlash name remains in common use as a generic term for microSD cards.<ref>{{cite web |last1=Williams |first1=Lynnae |title=TF Card: What Is It, And What's It Used For? |url=https://www.slashgear.com/1487273/what-is-tf-card-used-for/ |website=SlashGear |access-date=11 July 2025 |date=9 January 2024}}</ref> A passive adapter allows microSD cards to be used in standard SD card slots, maintaining backward compatibility across devices.

=== Increasing storage density ===
[[File:MicroSDXC.64GB.P1127589.jpg|thumb|upright|Back side of a microSD card, showing its eight electrical contacts]]

The storage capacity of SD cards increased steadily throughout the 2010s, driven by advances in NAND flash manufacturing and interface speeds. In January 2009, the SDA introduced the Secure Digital eXtended Capacity (SDXC) format, supporting up to 2&nbsp;TB of storage and transfer speeds up to 300&nbsp;MB/s.<ref>{{cite web |title=SDXC SIGNALS NEW GENERATION OF REMOVABLE MEMORY WITH UP TO 2 TERABYTES OF STORAGE |url=https://www.sdcard.org/cms/wp-content/uploads/2020/11/SD_Association_Announces_SDXC_Revised_1-7-09.pdf |website=sdcard.org |publisher=SD Association |access-date=30 December 2023 |archive-date=11 September 2024 |archive-url=https://web.archive.org/web/20240911012842/https://www.sdcard.org/cms/wp-content/uploads/2020/11/SD_Association_Announces_SDXC_Revised_1-7-09.pdf |url-status=live }}</ref> SDXC cards are formatted with the [[exFAT]] file system by default.<ref name="SDA Capacity" />

The first SDXC cards appeared in 2010, with early models offering capacities of 32 to 64&nbsp;GB and read/write speeds of several hundred megabits per second.<ref>{{cite web |url=http://www.dpreview.com/news/0903/09030601pretecsdxc.asp |title= Pretec introduces world's first SDXC card |work= Digital Photography Review |date= 2009-03-06 |access-date= 2010-08-22 |archive-date= 2010-08-21 |archive-url= https://web.archive.org/web/20100821022647/http://www.dpreview.com/news/0903/09030601pretecsdxc.asp |url-status= live}}</ref> Consumer adoption accelerated as digital cameras, smartphones, and card readers gained SDXC compatibility.

By 2011, manufacturers offered SDXC cards in 64 and 128&nbsp;GB capacities, with some models supporting UHS Speed Class 10 and faster.<ref>{{cite web |last=Conneally |first=Tim |date=2011-03-16 |title=Lexar ships 128&nbsp;GB Class 10 SDXC card; March 2011 |url=https://betanews.com/2011/03/16/lexar-ships-first-128gb-sdxc-cards |access-date=2024-01-22 |publisher=Betanews.com |archive-date=2023-11-11 |archive-url=https://web.archive.org/web/20231111195250/https://betanews.com/2011/03/16/lexar-ships-first-128gb-sdxc-cards/ |url-status=live}}</ref> In the following years, capacity milestones were reached at regular intervals: 256&nbsp;GB in 2013, 512&nbsp;GB in 2014, and 1&nbsp;TB in 2019.<ref>{{Cite web|url=https://www.theverge.com/2019/5/15/18626729/sandisks-1tb-microsd-card-available-b-h-photo-amazon-price|title=SanDisk's 1&nbsp;TB microSD card is now available|website=theverge.com|date=15 May 2019|access-date=19 December 2019|archive-date=17 June 2020|archive-url=https://web.archive.org/web/20200617090004/https://www.theverge.com/2019/5/15/18626729/sandisks-1tb-microsd-card-available-b-h-photo-amazon-price|url-status=live}}</ref>

The Secure Digital Ultra Capacity (SDUC) specification, announced in 2018, expanded maximum capacity to 128&nbsp;TB and increased theoretical transfer speeds to 985&nbsp;MB/s.<ref>{{cite web |title=SDUC Spec |url=https://www.sdcard.org/developers/overview/sdxc/ |access-date=2024-06-19}}</ref> In 2022, Kioxia previewed the first 2&nbsp;TB microSDXC card,<ref>{{Cite news |title=Представлена первая в мире карта памяти MicroSDXC ёмкостью 2 ТБ |url=https://www.ixbt.com/news/2022/09/29/predstavlena-pervaja-v-mira-karta-pamjati-microsdxc-jomkostju-2-tb.html |archive-url=https://web.archive.org/web/20250112031849/https://www.ixbt.com/news/2022/09/29/predstavlena-pervaja-v-mira-karta-pamjati-microsdxc-jomkostju-2-tb.html |archive-date=12 January 2025 |access-date=2025-04-03 |date=2022-09-29 |website=iXBT.com |language=ru-RU |url-status=live }}</ref> and in 2024, Western Digital announced the first 4&nbsp;TB SDUC card, scheduled for commercial release in 2025.<ref>{{Cite web |date=11 April 2024 |title=Western Digital Showcases New Super Speeds and Massive Capacities for M&E Workflows at NAB 2024 |url=https://www.westerndigital.com/company/newsroom/press-releases/2024/2024-04-11-western-digital-showcases-new-super-speeds-and-massive-capacities-at-nab-2024 |access-date=2025-06-19 |website=westerndigital.com |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911012946/https://www.westerndigital.com/company/newsroom/press-releases/2024/2024-04-11-western-digital-showcases-new-super-speeds-and-massive-capacities-at-nab-2024 |url-status=live}}</ref>

== Capacity standards ==
There are four defined SD capacity standards: Standard Capacity (SDSC), High Capacity (SDHC), Extended Capacity (SDXC), and Ultra Capacity (SDUC). In addition to specifying maximum storage limits, these standards also define preferred [[file system]]s for formatting cards.<ref name="SDA Capacity" /><ref name="SDA SDXC">{{cite web|title=Using SDXC|publisher=SD Association|url=http://www.sdcard.org/consumers/sdxc_capabilities/using_sdxc/|access-date=2011-12-08|archive-date=2014-10-10|archive-url=https://web.archive.org/web/20141010090939/https://www.sdcard.org/consumers/sdxc_capabilities/using_sdxc|url-status=dead}}</ref><ref>{{cite web|title=SDIO|publisher=SD Association|url=http://www.sdcard.org/developers/overview/sdio/|access-date=2011-12-08|archive-date=2020-05-20|archive-url=https://web.archive.org/web/20200520193351/https://www.sdcard.org/developers/overview/sdio/|url-status=live}}</ref>

{| class="wikitable" style="text-align:center;font-size:85%"
|+ Comparison of capacity standards<ref name="SDA Capacity" />
!
! scope="col" | SDSC
! scope="col" | SDHC
! scope="col" | SDXC
! scope="col" | SDUC
|- style="background: white;"
!Mark
| [[File:SD-Logo.svg|frameless|upright=0.25]]
| [[File:SDHC-Logo.svg|frameless|upright=0.25]]
| [[File:SDXC.svg|frameless|upright=0.25]]
| [[File:SDUC.svg|frameless|upright=0.25]]
|-
!Max capacity
| {{Nowrap|2 GB}}
| {{Nowrap|32 GB}}
| {{Nowrap|2 TB}}
| {{Nowrap|128 TB}}
|-
! scope="row" id="Filesys" | File system
| [[FAT12]], [[FAT16]]
| [[FAT32]]
| colspan="2" | [[exFAT]]
|}

=== SD (SDSC) ===
The original '''Secure Digital''' ('''SD''') card was introduced in 1999 as a successor to the MMC format. The name '''SD Standard Capacity''' ('''SDSC''') was applied later to distinguish it from newer variants. Although based on the same electrical interface as MMC, the SD format introduced several enhancements aimed at improving usability, durability, and performance:
* A notched, asymmetrical shape to prevent incorrect insertion.<ref name="Specification 1.01" />{{Rp|page=|pages=27-28}}
* Recessed electrical contacts to protect against damage and contamination.
* A four-line data bus for faster transfers, compared to MMC's single data line.<ref name="Specification 1.01" />{{Rp|page=17}}
* A mechanical write-protect switch.<ref name="Specification 1.01" />{{Rp|page=27}}
* These features came at the expense of increased card thickness: {{Convert|2.1|mm|abbr=on}} for standard SD cards, compared to {{Convert|1.4|mm|abbr=on}} for MMC. A 1.4&nbsp;mm '''Thin SD''' variant was also defined,<ref name="Specification 1.01" /> but saw little use.

SDSC cards support capacities up to 2&nbsp;GB{{efn|name="GiB"|reference=here, 1&nbsp;GB = 1 [[Byte#Units based on powers of 2|GiB]] = 2<sup>30</sup> B}} and use the [[FAT12]] or [[FAT16]] file system. They remain compatible with most SD-capable devices but have been largely superseded by higher-capacity formats.

Because of physical differences, full-size SD cards do not fit in slim MMC-only slots.

=== SDHC ===
'''SD High Capacity''' ('''SDHC''') was introduced in SD specification version 2.0, released in January 2006.<ref name="Specification 2.00" /> It expands the maximum capacity to 32&nbsp;GB, compared to the 2&nbsp;GB limit of SDSC.{{efn|name="GiB"|reference=here, 1&nbsp;GB = 1 [[Byte#Units based on powers of 2|GiB]] = 2<sup>30</sup> B}}<ref name="SDA Capacity" />

SDHC cards are physically identical to earlier standard-capacity SD (SDSC) cards, but differ in how they store and address data. This includes a redefinition of the Card-Specific Data (CSD) register (for details, see § [[#Storage capacity calculations|Storage capacity calculations]]). Additionally, SDHC cards are typically preformatted with the [[FAT32]] file system.

SDHC-compatible devices are required to support older SDSC cards. However, older SDSC devices may not recognize SDHC cards without a firmware update.<ref name="SDA Compatibility">{{cite web |title=SD Card Compatibility |url=https://www.sdcard.org/consumers/compatibility/ |access-date=2024-06-27 |publisher=SD Association |archive-date=November 21, 2011 |archive-url=https://web.archive.org/web/20111121065335/https://www.sdcard.org/consumers/compatibility/ |url-status=dead }}</ref> Older operating systems like Windows XP require patches or service packs to access SDHC cards.<ref>{{cite web |date=2008-02-15 |title=934428 – Hotfix for Windows XP that adds support for SDHC cards that have a capacity of more than 4&nbsp;GB |url=http://support.microsoft.com/kb/934428 |url-status=live |archive-url=https://web.archive.org/web/20100103175653/http://support.microsoft.com/kb/934428 |archive-date=2010-01-03 |access-date=2010-08-22 |work=Support |publisher=Microsoft}}</ref><ref>{{cite web |date=2008-05-15 |title=939772 – Some Secure Digital (SD) cards may not be recognized in Windows Vista |url=http://support.microsoft.com/kb/939772 |url-status=live |archive-url=https://web.archive.org/web/20100209062534/http://support.microsoft.com/kb/939772 |archive-date=2010-02-09 |access-date=2010-08-22 |work=Support |publisher=Microsoft}}</ref><ref>{{cite web |date=2008-02-21 |title=949126 – A Secure Digital High Capacity (SDHC) card is not recognized on a Windows Vista Service Pack 1-based computer |url=http://support.microsoft.com/kb/949126 |url-status=live |archive-url=https://web.archive.org/web/20100109134743/http://support.microsoft.com/kb/949126 |archive-date=2010-01-09 |access-date=2010-08-22 |work=Support |publisher=Microsoft}}</ref>

=== SDXC ===
'''SD eXtended Capacity''' ('''SDXC''') was introduced in SD specification version 3.01, released in January 2009.<ref name="Specification 3.01" /> It expands the maximum capacity to 2&nbsp;TB,{{efn|name="here, 1&nbsp;TB = 1024"|reference=here, 1&nbsp;TB = 1024<sup>4</sup> B}} compared to the 32&nbsp;GB{{efn|name="GiB"}} limit of SDHC. SDXC cards are formatted with the [[exFAT]] file system, which is required by the SDXC standard.<ref>{{Cite web |title=Capacity (SD/SDHC/SDXC) |url=https://www.sdcard.org/developers/overview/capacity/ |url-status=live |archive-url=https://web.archive.org/web/20111121064806/https://www.sdcard.org/developers/overview/capacity/ |archive-date=2011-11-21 |access-date=2017-03-20 |website=SD Association |language=en}}</ref><ref name="SDA Capacity">{{Cite web |date=2020-12-11 |title=Capacity (SD/SDHC/SDXC/SDUC) |url=https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |url-status=live |archive-url=https://web.archive.org/web/20240911012954/https://www.sdcard.org/developers/sd-standard-overview/capacity-sd-sdhc-sdxc-sduc/ |archive-date=2024-09-11 |access-date=2023-05-03 |website=SD Association |language=en-US}}</ref> While [[Windows Vista]] SP1 and later and [[OS X|Mac OS X]] 10.6.5 and later support exFAT natively,<ref>{{cite web |date=25 July 2008 |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) |url-status=live |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) |archive-date=2021-11-07 |access-date=2021-11-07 |website=[[Microsoft Docs]] |department=[[Microsoft TechNet|TechNet]]}}</ref><ref name="Apple Inc. 2011">{{cite web |date=2011-05-03 |title=About the SD and SDXC card slots |url=http://support.apple.com/kb/HT3553 |url-status=live |archive-url=https://web.archive.org/web/20110903100124/http://support.apple.com/kb/HT3553 |archive-date=2011-09-03 |access-date=2011-09-05 |publisher=Apple Inc.}}</ref><ref>{{cite web |date=2010-11-22 |title=Apple released exFAT support in OS X 10.6.5 update |url=http://www.tuxera.com/mac/apple-released-exfat-support-in-os-x-10-6-5-update/ |url-status=dead |archive-url=https://web.archive.org/web/20120513202527/http://www.tuxera.com/mac/apple-released-exfat-support-in-os-x-10-6-5-update/ |archive-date=2012-05-13 |access-date=2012-01-04 |publisher=Tuxera.com}}</ref> support in [[Berkeley Software Distribution|BSD]] and [[Linux]] distributions was limited until Microsoft released the exFAT specification and Linux kernel 5.4 included an open-source driver.<ref>{{cite web |url=https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.4-exFAT-Is-Coming |title=The Initial exFAT Driver Queued For Introduction With The Linux 5.4 Kernel |publisher=phoronix.com |date=2019-08-30 |access-date=2020-02-05 |archive-date=2019-12-18 |archive-url=https://web.archive.org/web/20191218061425/https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.4-exFAT-Is-Coming |url-status=live }}</ref>

SDXC cards can be reformatted to other file systems (e.g., [[ext4]], [[Unix File System|UFS]], [[VFAT]] or [[NTFS]]), which may improve compatibility with older devices or systems lacking exFAT support. Many SDHC-compatible hosts can use SDXC cards if reformatted to FAT32, but full compatibility is not guaranteed.<ref>{{cite web |title=Updated: How to upgrade your 3DS SD card, to 64&nbsp;GB and beyond |author=deKay |date=15 January 2015 |website=Lofi-Gaming |url=https://lofi-gaming.org.uk/blog/2013/10/25/updated-how-to-upgrade-your-3ds-sd-card-to-64gb-and-beyond/ |access-date=2018-12-21 |archive-date=2018-12-21 |archive-url=https://web.archive.org/web/20181221134714/https://lofi-gaming.org.uk/blog/2013/10/25/updated-how-to-upgrade-your-3ds-sd-card-to-64gb-and-beyond/ |url-status=live }}</ref><ref>{{cite web |title=Ask Hackaday: How On Earth Can A 2004 MP3 Player Read An SDXC Card? |first=Jenny |last=List |date=29 November 2017 |website=Hackaday |url=https://hackaday.com/2017/11/29/ask-hackaday-how-on-earth-can-a-2004-mp3-player-read-an-sdxc-card/ |access-date=2018-12-21 |archive-date=2018-12-21 |archive-url=https://web.archive.org/web/20181221182601/https://hackaday.com/2017/11/29/ask-hackaday-how-on-earth-can-a-2004-mp3-player-read-an-sdxc-card/ |url-status=live }}</ref><ref>{{cite web |title=High capacity microSD cards and Android – Gary explains |first=Gary |last=Sims |date=9 May 2016 |website=Android Authority |url=https://www.androidauthority.com/high-capacity-microsd-cards-android-gary-explains-690710/ |access-date=2018-12-21 |archive-date=2018-11-22 |archive-url=https://web.archive.org/web/20181122092400/https://www.androidauthority.com/high-capacity-microsd-cards-android-gary-explains-690710/ |url-status=live }}</ref>

=== SDUC ===
'''SD Ultra Capacity''' ('''SDUC''') was introduced in SD specification version 7.0, released in June 2018. It expands the maximum capacity to 128&nbsp;TB,{{efn|name="here, 1&nbsp;TB = 1024"}} compared to the 2&nbsp;TB limit of SDXC.<ref name="SDA PCIe NVMe" /> Like SDXC cards, SDUC cards use the exFAT file system by default.

== Bus marks ==
'''Bus marks''' indicate both the bus interface and the minimum data transfer performance of a device (as opposed to speed class ratings which indicate card performance) in terms of sustained sequential read and write speeds. These are most relevant for handling large files—such as photos and videos—where data is accessed in contiguous blocks. The SD specification has improved bus speed performance over time by increasing the clock frequency used to transfer data between the card and the host device. Regardless of the bus speed, a card may signal that it is "busy" while completing a read or write operation. Compliance with higher-speed bus standards typically reduces reliance on this "busy" signal, allowing for more efficient and continuous data transfers.

{| class="wikitable" style="text-align:center;font-size:85%"
|+ Comparison of bus speeds<ref name=":0">{{Cite web |date=2020-12-11 |title=Bus Speed (Default Speed/High Speed/UHS/SD Express) |url=https://www.sdcard.org/developers/sd-standard-overview/bus-speed-default-speed-high-speed-uhs-sd-express/ |access-date=2025-01-07 |website=SD Association |language=en-US}}</ref>
! rowspan="2" scope="colgroup" |Interface
! rowspan="2" |Mark
! colspan="3" |Bus
! colspan="4" scope="colgroup" | Capacity standard
! rowspan="2" scope="col" | {{Abbr|Spec|Specification(s)}}
|-
! scope="col" | Speed
! scope="col" | [[PCI Express|PCIe]]
! scope="col" | [[Duplex (telecommunications)|Duplex]]
! scope="col" | SD
! scope="col" | SDHC
! scope="col" | SDXC
! scope="col" | SDUC
|-
! scope="row" | Default
| {{N/a}}
| {{Nowrap|12.5 MB/s}}
| rowspan="8" {{N/a}}
| Half
| rowspan="2" {{Yes}}
| rowspan="11" {{Yes}}
| rowspan="11" {{Yes}}
| rowspan="11" {{Yes}}
| 1.01
|-
! scope="row" | {{Nowrap|High Speed}}
| {{N/a}}
| {{Nowrap|25 MB/s}}
|Half
| 1.10
|-
! scope="row" rowspan="2" | UHS-I
| rowspan="2" style="background:white" | [[File:UHS-I.svg|x20px]]
| {{Nowrap|50 MB/s}}
| rowspan="2" |Half
| rowspan="9" {{No}}
| rowspan="2" | 3.01
|-
| {{Nowrap|104 MB/s}}
|-
! scope="row" rowspan="2" | UHS-II
| rowspan="2" style="background:white" | [[File:UHS-II.svg|x20px]]
| {{Nowrap|156 MB/s}}
| Full
| rowspan="2" | 4.00,<br />4.10
|-
| {{Nowrap|312 MB/s}}
| Half
|-
! scope="row" rowspan="2" | UHS-III
| rowspan="2" style="background:white" | [[File:UHS-III.svg|x20px]]
| {{Nowrap|312 MB/s}}
| rowspan="2" | Full
| rowspan="2" | 6.00
|-
| {{Nowrap|624 MB/s}}
|-
! scope="row" rowspan="3" | SD Express
| rowspan="3" style="background:white" | [[File:SDex(short).svg|x20px]]
| {{Nowrap|985 MB/s}}
| {{Nowrap|3.1 ×1}}
| rowspan="3" {{N/a}}
| 7.00,<br />7.10
|-
| {{Nowrap|1,969 MB/s}}
| {{Nowrap|3.1 ×2}}, {{Nowrap|4.0 ×1}}
| rowspan="2"| 8.0
|-
| {{Nowrap|3,938 MB/s}}
| {{Nowrap|4.0 ×2}}
|}
{| class="wikitable" style="text-align:center;font-size:85%"
|+Bus speed of host and card combinations (in MB/s)<ref name="SDA PCIe NVMe">{{Cite journal|date=June 2018|title=SD Express Cards with Pie and Name Interfaces|url=https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf|journal=SD Association|pages=9|access-date=2018-06-27|archive-date=2020-11-12|archive-url=https://web.archive.org/web/20201112011753/https://www.sdcard.org/downloads/pls/latest_whitepapers/SD_Express_Cards_with_PCIe_and_NVMe_Interfaces_White_Paper.pdf|url-status=dead}}</ref>
! colspan="2" rowspan="2" {{Diagonal split header 2|Card|Host}}
! colspan="2" | UHS-I
! colspan="2" | UHS-II
! rowspan="2" | UHS-III
! rowspan="2" | Express
|-
! UHS50
! UHS104
! {{Abbr|Full|Full-duplex}}
! {{Abbr|Half|Half-duplex}}
|-
! rowspan="2" |UHS-I
! UHS50
|'''{{0|0}}50'''
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|{{0|0}}50
|-
! UHS104
|{{0|0}}50
|'''104'''
|104
|104
|104
|104
|-
! rowspan="2" |UHS-II
! {{Abbr|Full|Full-duplex}}
|{{0|0}}50
|104
|'''156'''
|156
|156
|156
|-
! {{Abbr|Half|Half-duplex}}
|{{0|0}}50
|104
|156
|'''312'''
|312
|312
|-
! colspan="2" |UHS-III
|{{0|0}}50
|104
|156
|312
|'''624'''
|624
|-
! colspan="2" |Express
|{{0|0}}50
|104
|104
|104
|104
|'''3,938'''
|}

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

=== High Speed ===
With version 1.10 of the specification, the SD Association introduced '''High-Speed''' mode, which increased the maximum transfer rate to 25&nbsp;MB/s. This enhancement was designed to meet the growing performance requirements of devices such as digital cameras.<ref name="SDA Bus Speed" />

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

The '''Ultra High Speed''' ('''UHS''') bus interface enables faster data transfer on SDHC, SDXC and SDUC cards.<ref name="SDA Bus Speed">{{cite web |url=https://www.sdcard.org/developers/overview/bus_speed/ |title=Bus Speed (Default Speed/ High Speed/ UHS) |publisher=SD Association |access-date=2013-11-13 |archive-date=2016-10-04 |archive-url=https://web.archive.org/web/20161004053633/https://www.sdcard.org/developers/overview/bus_speed/ |url-status=live }}</ref><ref>{{cite web |url=https://www.engadget.com/2010/06/24/sd-cards-branded-with-an-upper-case-i-are-faster-yo/ |title=SD cards branded with an upper-case 'I' are faster, yo |publisher=Engadget |date=2010-06-24 |access-date=2010-08-22 |archive-date=2010-08-28 |archive-url=https://web.archive.org/web/20100828145021/http://www.engadget.com/2010/06/24/sd-cards-branded-with-an-upper-case-i-are-faster-yo/ |url-status=live }}</ref>

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

To achieve higher transfer speeds, UHS cards and devices use specialized electrical signaling and hardware interfaces. UHS-I cards operate at 1.8&nbsp;V instead of the standard 3.3&nbsp;V and use a four-bit transfer mode. UHS-II and UHS-III introduce a second row of interface pins to add a second lane of data transfer and use [[low-voltage differential signaling]] (LVDS) at 0.4&nbsp;V to increase speed and reduce power consumption and electromagnetic interference (EMI).<ref>{{cite web |title=SD Standard Overview |url=https://www.sdcard.org/developers/sd-standard-overview/ |website=SD Association |date=2020-12-11 |access-date=2023-06-19}}</ref><ref name=":0" />

The following UHS speed classes are defined:

==== UHS-I ====
Support for the UHS-I interface was introduced in SD specification version 3.01, released in May 2010. This version added several new transfer modes: '''SDR50''', which uses a 100&nbsp;MHz clock with single data rate signaling to reach up to 50&nbsp;MB/s; '''DDR50''', a [[double data rate]] mode at 50&nbsp;MHz that transfers data on both clock edges for up to 50&nbsp;MB/s; and '''SDR104''', which increases the clock speed to 208&nbsp;MHz, enabling transfer rates up to 104&nbsp;MB/s.<ref name="Specification 3.01" />

In 2018, SanDisk developed a proprietary mode unofficially known as '''DDR200''', which combines double data rate signaling with a 208&nbsp;MHz clock to achieve read speeds of up to 170&nbsp;MB/s without requiring additional pins. Write speeds remain limited to 104&nbsp;MB/s, similar to SDR104. These higher speeds are typically used when offloading data from cards via specialized readers.<ref>{{Cite web |date=2022 |title=SanDisk QuickFlow Technology tech brief |url=https://documents.sandisk.com/content/dam/asset-library/en_us/assets/public/western-digital/collateral/tech-brief/tech-brief-sandisk-quickflow-technology.pdf |access-date=14 July 2025 |website=SanDisk}}</ref><ref>{{cite web |title=GL3232 |url=http://www.genesyslogic.com/en/product_view.php?show=83 |url-status=live |archive-url=https://web.archive.org/web/20200921071215/http://www.genesyslogic.com/en/product_view.php?show=83 |archive-date=2020-09-21 |access-date=2021-02-04 |website=Genesys Logic}}</ref> In 2022, SanDisk introduced '''DDR225''', further increasing performance to up to 200&nbsp;MB/s read and 140&nbsp;MB/s write. Although neither mode is officially part of the SD specification, although they have been adopted by several other manufacturers.<ref>{{Cite web |title=Lexar Professional 1066x microSDXC UHS-I Card SILVER Series |url=https://www.lexar.com/portfolio_page/professional-1066x-microsdhcmicrosdxc-uhs-i-cards-silver-series/ |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 |access-date=2021-04-10 |website=Lexar |language=en}}</ref><ref>{{Cite web |title=Canvas Go! Plus Class 10 microSD Cards – V30, A2 – 64&nbsp;GB–512&nbsp;GB |url=https://www.kingston.com/en/memory-cards/canvas-go-plus-microsd-card |access-date=2021-04-10 |website=Kingston Technology Company |language=en-US}}</ref>

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

Support for the UHS-II interface was introduced in SD specification version 4.0, released in January 2011. It added two new transfer modes: '''FD156''', supporting up to 156&nbsp;MB/s full-[[Duplex (telecommunications)|duplex]], and '''HD312''', enabling up to 312&nbsp;MB/s half-duplex. These speeds required a second row of connectors for LVDS, bringing the total to 17 for full-size cards and 16 for microSD cards.<ref name="SDA Bus Speed" /><ref>{{cite web |date=5 January 2011 |title=Association Triples Speeds with UHS-II |url=https://www.sdcard.org/press/SD_Association_Announces_UHS-II_eBOOK_Jan_5_2011_ENGLISH.PDF |url-status=dead |archive-url=https://web.archive.org/web/20110321195143/http://www.sdcard.org/press/SD_Association_Announces_UHS-II_eBOOK_Jan_5_2011_ENGLISH.PDF |archive-date=2011-03-21 |access-date=2011-08-09 |publisher=SD Card}}</ref> 

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

While initial adoption began in cameras around 2014, wider implementation took several more years, as few applications required the extra speed provided by the interface.<ref name=":1">{{Cite web |last=Cunningham |first=Andrew |date=2025-04-03 |title=Explaining MicroSD Express cards and why you should care about them |url=https://arstechnica.com/gadgets/2025/04/what-is-microsd-express-and-why-is-it-mandatory-for-the-nintendo-switch-2/ |access-date=2025-06-30 |website=Ars Technica |language=en}}</ref> {{As of|2025}}, only about 100 cameras, mostly high-end models, support UHS-II cards.<ref>{{cite web |title=UHS-II camera list |url=https://www.memorycard-lab.com/-Article/UHS-II-Cameras |access-date=2025-01-04 |publisher=memorycard-lab.com}}</ref>

==== UHS-III ====
Support for the UHS-III interface was introduced in SD specification version 6.0, released in February 2017. It added two new full-duplex transfer modes: '''FD312''', offering up to 312&nbsp;MB/s, and '''FD624''', doubling that to 624&nbsp;MB/s.<ref name="Specification 6.00" /> UHS-III retains the same physical interface and pin layout as UHS-II for backward compatibility.<ref>{{Cite web |date=23 February 2017 |title=SD Association Doubles Bus Interface Speeds with UHS-III |url=https://www.sdcard.org/press/DoublesTransferSpeeds_with_UHS3_2_9_2017.pdf |url-status=dead |archive-url=https://web.archive.org/web/20170224211349/https://www.sdcard.org/press/DoublesTransferSpeeds_with_UHS3_2_9_2017.pdf |archive-date=24 February 2017 |access-date=23 February 2017}}</ref> However, {{As of|2025|lc=y}}, UHS-III has seen limited adoption and is unlikely to be widely implemented, as the SDA instead prioritizes SD Express, which offers even higher transfer rates but limits backward compatibility to UHS-I speeds.<ref>{{Cite web |last=Cunningham |first=Andrew |date=2024-02-28 |title=Speedy “SD Express” cards have gone nowhere for years, but Samsung could change that |url=https://arstechnica.com/gadgets/2024/02/sd-express-cards-from-samsung-promise-faster-than-sata-speeds-for-microsd-devices/ |access-date=2025-06-30 |website=Ars Technica |language=en}}</ref><ref>{{Cite AV media |url=https://www.youtube.com/watch?v=HtgIHfqQiC8 |title=Explaining SD Cards |date=2025-01-05 |last=Barnatt |first=Christopher |type=Video |series=ExplainingComputers |access-date=2025-06-30 |via=YouTube}}</ref>

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

SD Express was introduced in SD specification version 7.0, released in June 2018. By incorporating a single [[PCI Express 3.0]] (PCIe) lane and supporting the [[NVM Express]] (NVMe) storage protocol, SD Express enables full-duplex transfer speeds of up to 985&nbsp;MB/s. SD Express cards support [[direct memory access]] (DMA), which can improve performance, though security researchers have warned that it may also increase the attack surface in the event of a compromised or malicious card.<ref>{{cite web |date=May 19, 2022 |title=When microSD Cards Turn Against You |url=https://research.nccgroup.com/2022/05/19/when-microsd-cards-turn-against-you/ |website=NCC Group}}</ref> Compatible cards must support both PCIe and NVMe, and may be formatted as SDHC, SDXC, or SDUC. For backward compatibility, SD Express cards are also required to support the High-Speed and UHS-I bus interfaces. However, because the PCIe interface reuses the second row of pins previously used by UHS-II and UHS-III, compatibility with older devices is limited to UHS-I speeds. The specification also reserves space for two additional pins for future use.<ref>{{cite web |date=June 27, 2018 |title=SD Express Card Spec Announced – PCIe + NVMe Up To 985&nbsp;MB/s |url=https://www.anandtech.com/show/12902/sd-express-card-spec-announced-pcie-nvme-up-to-985mbs |url-status=dead |archive-url=https://web.archive.org/web/20250412032606/https://www.anandtech.com/show/12902/sd-express-card-spec-announced-pcie-nvme-up-to-985mbs |archive-date=12 April 2025 |access-date=12 April 2025 |website=AnandTech}}</ref>

In February 2019, the SD Association introduced microSD Express,<ref>{{cite news |last=Gartenberg |first=Chain |date=25 February 2019 |title=Memory cards are about to get much faster with new microSD Express spec |url=https://www.theverge.com/circuitbreaker/2019/2/25/18239558/microsd-express-sd-association-new-format-speed-faster-mwc-2019-data-transfer |url-status=live |archive-url=https://web.archive.org/web/20190315212414/https://www.theverge.com/circuitbreaker/2019/2/25/18239558/microsd-express-sd-association-new-format-speed-faster-mwc-2019-data-transfer |archive-date=15 March 2019 |access-date=18 March 2019 |work=The Verge}}</ref> along with updated visual marks to help users identify compatible cards and devices.<ref>{{cite news |last=Henchman |first=Mark |date=25 February 2019 |title=The microSD Express standard combines PCI Express speeds, microSD convenience |url=https://www.pcworld.com/article/3343067/the-microsd-express-standard-combines-pci-express-speeds-microsd-convenience.html |url-status=live |archive-url=https://web.archive.org/web/20190808085536/https://www.pcworld.com/article/3343067/the-microsd-express-standard-combines-pci-express-speeds-microsd-convenience.html |archive-date=8 August 2019 |access-date=18 March 2019}}</ref>

SD specification version 8.0, released in May 2020, expanded the interface to support [[PCIe 4.0]] and introduced dual-lane configurations for full-size cards by adding a third row of electrical contacts, bringing the total to 26. This raised the theoretical maximum transfer rate to 3,938&nbsp;MB/s using dual-lane PCIe 4.0.<ref>{{Cite press release |title=SDExpress Delivers New Gigabtye Speeds For SDMemory Cards |publisher=SD association |url=https://www.sdcard.org/press/whatsnew/SDExpressDeliversNewGigabtyeSpeedsForSDMemoryCards.pdf |access-date=2020-05-19 |url-status=live |archive-url=https://web.archive.org/web/20200520193348/https://www.sdcard.org/press/whatsnew/SDExpressDeliversNewGigabtyeSpeedsForSDMemoryCards.pdf |archive-date=2020-05-20 |work=SD card}}</ref> Due to space constraints, the microSD form factor cannot accommodate a third row of contacts and remains limited to a single PCIe lane.

Adoption has been gradual. In February 2024, [[Samsung]] began sampling its first microSD Express cards,<ref>{{Cite web |last=Cunningham |first=Andrew |date=2024-02-28 |title=Speedy "SD Express" cards have gone nowhere for years, but Samsung could change that |url=https://arstechnica.com/gadgets/2024/02/sd-express-cards-from-samsung-promise-faster-than-sata-speeds-for-microsd-devices/ |url-status=live |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/ |archive-date=9 April 2025 |access-date=2025-04-09 |website=Ars Technica |language=en-US}}</ref> though commercial availability remained limited. Interest grew in April 2025 when Nintendo announced that the [[Nintendo Switch 2|Switch 2]] would support only microSD Express cards, with UHS-I card support limited to transferring media from earlier models.<ref>{{Cite web |last=Anderson |first=Robert |date=2025-04-04 |title=You Can Already Buy Switch 2 Compatible MicroSD Express Cards |url=https://www.ign.com/articles/nintendo-switch-2-microsd-express-cards-where-to-buy |access-date=2025-04-09 |website=IGN |language=en}}</ref>

{{As of|2025|6}}, only single-lane PCIe 3.1 SD Express cards are commercially available; no PCIe 4.0 or dual-lane cards have been released for general sale.<ref name=":1" /><ref>{{Cite AV media |url=https://www.youtube.com/watch?v=eLUrpGMVcl4 |title=Testing MicroSD Express: Very Fast SD Storage |date=2025-06-29 |last=Barnatt |first=Christopher |type=Video |publisher=ExplainingComputers |access-date=2025-06-30 |via=YouTube}}</ref>

== Card speed class ratings ==
{| class="wikitable" style="margin-left:1em; float:right; text-align:center; font-size:85%"
|+ Comparison of card speed class ratings<ref>{{Cite web |date=2020-12-11 |title=Speed Class {{!}} SD Association |url=https://www.sdcard.org/developers/sd-standard-overview/speed-class/ |access-date=2025-01-07 |website=www.sdcard.org |language=en-US |archive-date=4 January 2025 |archive-url=https://web.archive.org/web/20250104004951/https://www.sdcard.org/developers/sd-standard-overview/speed-class/ |url-status=live }}</ref>
! scope="col" rowspan="2" | {{Abbr|Min speed|Minimum serial data writing speed}}
! scope="colgroup" colspan="4" | Speed Class
! scope="colgroup" colspan="4" | [[Video format]]{{Efn|The necessary recording and playback speed class requirements may vary by device.}}
|-
! scope="col" | Original
! scope="col" | UHS
! scope="col" | Video
! scope="col" | SD Express
! scope="col" | [[Standard-definition television|SD]]
! scope="col" | [[High-definition video|HD]]
! scope="col" | [[4K resolution|4K]]
! scope="col" | [[8K resolution|8K]]
|-
! scope="row" | {{Nowrap|2 MB/s}}
| style="background:white" | {{Nowrap|Class 2 (C2)}}<br />[[File:SDHC Speed Class 2.svg|x20px]]
| rowspan="3" {{N/a}}
| rowspan="2" {{N/a}}
| rowspan="7" {{N/a}}
| rowspan="11" {{Yes}}
| {{No}}
| rowspan="2" {{No}}
| rowspan="4" {{No}}
|-
! scope="row" | {{Nowrap|4 MB/s}}
| style="background:white" | {{Nowrap|Class 4 (C4)}}<br />[[File:SDHC Speed Class 4.svg|x20px]]
| rowspan="10" {{Yes}}
|-
! scope="row" | {{Nowrap|6 MB/s}}
| style="background:white" | {{Nowrap|Class 6 (C6)}}<br />[[File:SDHC Speed Class 6.svg|x20px]]
| style="background:white" | {{Nowrap|Class 6 (V6)}}<br />[[File:SD Video Speed Class 6.svg|x20px]]
| rowspan="9" {{Yes}}
|-
! scope="row" | {{Nowrap|10 MB/s}}
| style="background:white" | {{Nowrap|Class 10 (C10)}}<br />[[File:SDHC Speed Class 10.svg|x20px]]
| style="background:white" | {{Nowrap|Class 1 (U1)}}<br />[[File:SD UHS Speed Class 1.svg|x20px]]
| style="background:white" | {{Nowrap|Class 10 (V10)}}<br />[[File:SD Video Speed Class 10.svg|x20px]]
|-
! scope="row" | {{Nowrap|30 MB/s}}
| rowspan="7" {{N/a}}
| style="background:white" | {{Nowrap|Class 3 (U3)}}<br />[[File:SD UHS Speed Class 3.svg|x20px]]
| style="background:white" | {{Nowrap|Class 30 (V30)}}<br />[[File:SD Video Speed Class 30.svg|x20px]]
| rowspan="7" {{Yes}}
|-
! scope="row" | {{Nowrap|60 MB/s}}
| rowspan="6" {{N/a}}
| style="background:white" | {{Nowrap|Class 60 (V60)}}<br />[[File:SD Video Speed Class 60.svg|x20px]]
|-
! scope="row" | {{Nowrap|90 MB/s}}
| style="background:white" | {{Nowrap|Class 90 (V90)}}<br />[[File:SD Video Speed Class 90.svg|x20px]]
|-
! scope="row" | {{Nowrap|150 MB/s}}
| rowspan="4" {{N/a}}
| style="background:white" | {{Nowrap|Class 150 (E150)}}<br />[[File:SD Express Class 150.svg|41x41px]]
|-
! scope="row" | {{Nowrap|300 MB/s}}
| style="background:white" | {{Nowrap|Class 300 (E300)}}<br />[[File:SD Express Class 300.svg|41x41px]]
|-
! scope="row" | {{Nowrap|450 MB/s}}
| style="background:white" | {{Nowrap|Class 450 (E450)}}<br />[[File:SD Express Class 450.svg|41x41px]]
|-
! scope="row" | {{Nowrap|600 MB/s}}
| style="background:white" | {{Nowrap|Class 600 (E600)}}<br />[[File:SD Express Class 600.svg|41x41px]]
|}
'''Speed Class ratings''' were introduced to indicate the minimum data transfer performance of an SD card (as opposed to bus speed rating, which indicates device performance) in terms of sustained sequential write performance. This performance is important when transferring large files, especially during tasks like video recording, which requires consistent throughput to avoid dropped frames.<ref name="SDA Speed Class" />

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

=== Original speed class (C) ===
The original speed class ratings—Class 2, 4, 6, and 10—specify minimum sustained write speeds of 2, 4, 6, and 10&nbsp;MB/s, respectively. Class 10 cards assume a non-fragmented file system and use the High Speed bus mode.<ref name="Specification 3.01" /> These are represented by a number encircled with a "C" (e.g., C2, C4, C6 and C10).

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

=== Video speed class (V) ===
Video speed class ratings—V6, V10, V30, V60, and V90—specify minimum sustained write speeds of 6, 10, 30, 60, and 90&nbsp;MB/s, respectively.<ref name="SDA Video Speed">{{cite web |date=2016-02-26 |title=NEW SD ASSOCIATION VIDEO SPEED CLASS SUPPORTS 8K AND MULTI-FILE VIDEO RECORDING |url=https://www.sdcard.org/press/New_SD_Association_Speed_Class_Supports_8K_and_Multi_File_Video_Recording.pdf |url-status=dead |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 |archive-date=2016-03-07 |access-date=2016-03-03 |publisher=SD Association}}</ref><ref name="SDA Speed Class" /><ref name="SDA Speed Class Consumer">{{cite web |date=11 December 2020 |title=Speed Class Standards for Video Recording – SD Association |url=https://www.sdcard.org/consumers/choices/speed_class/index.html |url-status=live |archive-url=https://web.archive.org/web/20160407123207/https://www.sdcard.org/consumers/choices/speed_class/index.html |archive-date=7 April 2016 |access-date=28 April 2016 |website=sdcard.org}}</ref><ref>{{cite web |last=Chaundy |first=Fabian |date=2016-02-26 |title=New Video Speed Class for SD Cards |url=https://www.cinema5d.com/new-video-speed-class-for-sd-cards/ |url-status=live |archive-url=https://web.archive.org/web/20160307015103/https://www.cinema5d.com/new-video-speed-class-for-sd-cards/ |archive-date=2016-03-07 |access-date=2016-03-03 |work=cinema5D}}</ref> These classes are represented by a stylized "V" followed by the number and were introduced to support high-resolution formats such as 4K and [[Ultra-high-definition television|8K]] and to align with the performance characteristics of [[multi-level cell]] NAND flash memory.<ref>{{cite web |date=February 2016 |title=Video Speed Class: The new capture protocol of SD 5.0 |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Video_Speed_Class-The_new_capture_protocol_of_SD_5.0.pdf |url-status=dead |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 |archive-date=2016-12-23 |access-date=2016-03-03 |publisher=SD Association}}</ref><ref>{{cite web |last=Shilov |first=Anton |date=2016-03-01 |title=SD Association Announces SD 5.0 Specification: SD Cards For UHD and 360° Video Capture |url=http://www.anandtech.com/show/10105/sd-association-announces-50-specification |url-status=dead |archive-url=https://web.archive.org/web/20160303190529/http://www.anandtech.com/show/10105/sd-association-announces-50-specification |archive-date=2016-03-03 |access-date=2016-03-03 |publisher=Anand Tech}}</ref>

=== SD Express Speed Class (E) ===
SD Express speed class ratings—E150, E300, E450, and E600—specify minimum sustained write speeds of 150, 300, 450, and 600&nbsp;MB/s, respectively.<ref name="Pinto 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}}</ref> These classes are represented by a stylized "E" followed by the number, enclosed in a rounded rectangle. They are designed for data-intensive applications such as large-scale video processing, real-time analytics, and software execution.<ref name="Pinto 2023" />

=== "×" rating ===
{| class="wikitable" style="margin-left:1em; float:right; text-align:center; font-size:85%"
! valign="top" | Rating
! valign="top" | Approx.<br />(MB/s)
! valign="top" | Comparable<br />speed class
|-
| 16×
| 2.34
| style="background:white" | [[File:SDHC Speed Class 2.svg|28px]] (13×)
|-
| 32×
| 4.69
| style="background:white" | [[File:SDHC Speed Class 4.svg|28px]] (27×)
|-
| 48×
| 7.03
| style="background:white" | [[File:SDHC Speed Class 6.svg|28px]] (40×)
|-
| 100×
| 14.6
| style="background:white" | [[File:SD Class 10.svg|28px]] (67×)
|}
{{Main|CD and DVD writing speed}}
Initially, some manufacturers used a "×" rating system based on the speed of a standard [[Optical disc drive|CD-ROM drive]] (150&nbsp;kB/s or 1.23&nbsp;[[Mbit/s]]),{{efn|reference=1 KB = 1024 B}} but this approach was inconsistent and often unclear. It was later replaced by standardized Speed Class systems that specify guaranteed minimum write speeds.<ref name="Specification 3.01" /><ref name="SDA Speed Class Consumer" /><ref>{{Cite web |title=SD Standards Brochure 2017 |url=https://www.sdcard.org/consumers/pdf/2017SDA_brochure_eng.pdf |url-status=dead |archive-url=https://web.archive.org/web/20170330174639/https://www.sdcard.org/consumers/pdf/2017SDA_brochure_eng.pdf |archive-date=2017-03-30 |access-date=2017-03-29}}</ref><ref>{{cite web |title=Flash Memory Cards and X-Speed Ratings |url=http://www.kingston.com/us/flash/x-speed |url-status=dead |archive-url=https://web.archive.org/web/20170702204220/http://www.kingston.com/us/flash/x-speed |archive-date=2017-07-02 |access-date=2017-08-05 |publisher=Kingston}}</ref>

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

In some cases, cards of the same speed class may perform very differently. For instance, random small-file write speeds can be significantly lower than sequential performance. A 2012 study found some Class 2 cards outperformed Class 10 cards in random writes.<ref name="Kim, Agrawal & Ungureanu 2012">{{cite conference |last1=Kim |first1=H. |last2=Agrawal |first2=N. |last3=Ungureanu |first3=C. |date=2012-01-30 |title=Revisiting Storage for Smartphones |url=http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf |conference=USENIX Conference on File and Storage Technologies (FAST) |publisher=NEC Laboratories America |archive-url=https://web.archive.org/web/20121010194100/http://static.usenix.org/events/fast/tech/full_papers/Kim.pdf |archive-date=2012-10-10 |access-date=2012-12-27 |quote=Speed class considered irrelevant: our benchmarking reveals that the "speed class" marking on SD cards is not necessarily indicative of application performance; although the class rating is meant for sequential performance, we find several cases in which higher-grade SD cards performed worse than lower-grade ones overall.}}</ref> Another test in 2014 reported a 300-fold difference in small-write performance across cards, with a Class 4 card outperforming higher-rated cards in certain use cases.<ref name="Lui 2014">{{cite web |last=Lui |first=Gough |date=2014-01-16 |title=SD Card Sequential, Medium & Small Block Performance Round-Up |url=http://goughlui.com/2014/01/16/testing-sd-card-performance-round-up/ |archive-url=https://web.archive.org/web/20151208112031/http://goughlui.com/2014/01/16/testing-sd-card-performance-round-up/ |archive-date=2015-12-08 |access-date=2015-11-29 |website=Gough's techzone |quote=Variations in 4k small block performance saw a difference of approximately 300-fold between the fastest and slowest cards. Distressingly, many of the tested cards were mediocre to poor on that metric, which may explain why running updates on Linux running off SD cards can take a very long time.}}</ref>

== Performance ratings ==
{| class="wikitable" style="margin-left:1em; float:right; text-align:center; font-size:85%"
|+Comparison of Application Performance Class ratings<ref>{{Cite web |date=2020-12-11 |title=Application Performance Class |url=https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |url-status=live |archive-url=https://web.archive.org/web/20211103014547/https://www.sdcard.org/developers/sd-standard-overview/application-performance-class/ |archive-date=3 November 2021 |access-date=2025-01-07 |website=[[SD Association]] |language=en-US}}</ref>
! rowspan="2" |Rating
! colspan="2" |Minimum random [[IOPS]]
! rowspan="2" |Minimum sustained<br />sequential writing
|-
!Read
!Write
|-
| style="background:white" |{{Nowrap|Class 1 (A1)}}<br />[[File:SD App Performance 1.svg|41x41px]]
|1,500
|500
| rowspan="2" |{{Nowrap|10 MB/s}}
|-
| style="background:white" |{{Nowrap|Class 2 (A2)}}<br />[[File:SD App Performance 2.svg|41x41px]]
|4,000
|2,000
|}

'''Application Performance Class''' ratings were introduced in 2016 to identify SD cards capable of reliably running and storing applications, alongside general-purpose tasks such as saving photos, videos, music, and documents.

Earlier SD card speed ratings focused on sequential read and write performance, which is important when transferring large files. However, running apps and operating systems involves frequent access to many small files—a pattern known as [[random access]]—which places different demands on storage.<ref name="Geerling 2019">{{Cite web |last=Geerling |first=Jeff |date=July 22, 2019 |title=A2-class microSD cards offer no better performance for the Raspberry Pi |url=https://www.jeffgeerling.com/blog/2019/a2-class-microsd-cards-offer-no-better-performance-raspberry-pi |access-date=2025-06-05 |website=jeffgeerling.com}}</ref> Before the introduction of the Application Performance Classes, random access performance could vary significantly between cards and presented a limiting factor in some use cases.<ref name="Kim, Agrawal & Ungureanu 2012" /><ref name="Lui 2014" /><ref>{{cite web |title=Raspberry Pi forum: SD card benchmarks |url=http://www.raspberrypi.org/forums/viewtopic.php?t=4076 |url-status=live |archive-url=https://web.archive.org/web/20140813011920/http://www.raspberrypi.org/forums/viewtopic.php?t=4076 |archive-date=2014-08-13 |access-date=2014-08-12}}</ref>

As SD cards saw broader use for app storage and system boot volumes—especially in mobile devices, [[single-board computer]]s, and embedded systems—a new performance metric became necessary.<ref name="Geerling 2019" /> This need became more pressing with Android's [[Adoptable Storage]] feature, which allows SD cards to function as internal (non-removable) storage on smartphones and tablets.<ref>{{Cite web |title=Adoptable storage |url=https://source.android.com/docs/core/storage/adoptable |url-status=live |archive-url=https://web.archive.org/web/20250412032605/https://source.android.com/docs/core/storage/adoptable |archive-date=2025-04-12 |access-date=2025-04-12 |website=Android Open Source Project |language=en}}</ref>

To address this, the SD Association introduced Application Performance Classes. The first, A1, defined in SD Specification 5.1 (released November 2016), requires a minimum of 1,500 input/output operations per second ([[IOPS]]) for reading and 500 IOPS for writing, using 4&nbsp;kB blocks. The higher-tier A2 class, defined in Specification 6.0 (released in February 2017), raises the thresholds to 4,000 read and 2,000 write IOPS. However, achieving these speeds requires host device support for [[command queuing]] and [[Cache (computing)|write caching]], features that allow the card to optimize the execution of multiple simultaneous tasks and temporarily store data.<ref name="Pinto 2017">{{Cite web |last=Pinto |first=Yosi |date=2017-03-24 |title=Applications in Action: Introducing the Newest Application Performance Class |url=https://www.sdcard.org/press/thoughtleadership/applications-in-action-introducing-the-newest-application-performance-class/ |access-date=2025-06-20 |website=SD Association |language=en-US}}</ref> If not properly supported, performance will fall back to A1 levels. Both A1 and A2 cards must also sustain a minimum sequential write speed of 10&nbsp;MB/s, equivalent to speed classes C10, U1 and V10.<ref>{{Cite web |date=November 2016 |title=Application Performance Class: The new class of performance for applications on SD memory cards (SD 5.1) |url=https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |url-status=live |archive-url=https://web.archive.org/web/20161123202004/https://www.sdcard.org/downloads/pls/latest_whitepapers/Application_Peformance_Class_White_Paper.pdf |archive-date=2016-11-23 |access-date=2024-09-11 |website=[[SD Association]]}}</ref>

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

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

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

Most full-size SD cards have a mechanical write-protect switch, a sliding tab over a notch on the left side (viewed from the top, with the beveled corner on the right), that signals to the device to treat the card as read-only. Sliding the tab up (toward the contacts) sets the card to read/write; sliding it down sets it to read-only. However, the switch position is not detected by the card's internal circuitry.<ref name="Specification 9.00" /> Therefore, some devices ignore it, while others allow overrides.<ref>{{Cite web |date=2006-09-25 |title=SD Specifications Part 1 Physical Layer Simplified Specification |url=https://users.ece.utexas.edu/~valvano/EE345M/SD_Physical_Layer_Spec.pdf |url-status=live |access-date=2025-11-03 |website=SD Group}}</ref>

MiniSD and microSD cards lack a built-in notch but can be used with adapters that include one. Cards without a notch are always writable; cards with preloaded content have a notch but no sliding tab.<ref>{{Cite web |date=2022-10-07 |title=Secure Digital |url=https://encyclopedia.pub/entry/28360 |url-status=live |access-date=2025-11-03 |website=encyclopedia.pub}}</ref>

==== Card password ====
A host device can lock an SD card using a password of up to 16 bytes, typically supplied by the user.<ref>{{Cite web |title=Memory Card Control Layer |url=https://www.keil.com/pack/doc/mw/filesystem/html/mc_control_layer.html |url-status=live |access-date=2025-11-03 |website=www.keil.com}}</ref> 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.<ref>{{Cite web |date=2017-04-10 |title=SD Specifications Part 1 Physical Layer Simplified Specification |url=https://academy.cba.mit.edu/classes/networking_communications/SD/SD.pdf |url-status=live |access-date=2025-11-03 |website=Technical Committee SD Card Association}}</ref>

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

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

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

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

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

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

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

=== Vendor enhancements ===
[[File:Eye-Fi Wifi Card.jpg|thumb|[[Eye-Fi]] Mobi 16&nbsp;GB card with integrated Wi-Fi]]
[[File:USB-SD-Cards.jpg|thumb|SD cards with dual interfaces: SD and [[USB]]]]

Vendors have sought to differentiate their products in the market through various vendor-specific features:
* '''Integrated Wi-Fi''' – Several companies produce SD cards with built-in [[Wi-Fi]] transceivers. 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. Some models [[Geotagging|geotag]] their pictures.
* '''Pre-loaded content''' – In 2006, SanDisk announced [[Gruvi]], a microSD card with extra digital rights management features, which they intended as a medium for publishing content. SanDisk again announced pre-loaded cards in 2008, under the [[slotMusic]] name, this time not using any of the DRM capabilities of the SD card.<ref>{{cite web |last=Robson |first=Wayde |url=http://www.audioholics.com/news/industry-news/sandisk-slotmusic |title=AudioHolics |date=22 September 2008 |publisher=AudioHolics |access-date=2014-01-02 |archive-date=2013-06-02 |archive-url=https://web.archive.org/web/20130602015817/http://www.audioholics.com/news/industry-news/sandisk-slotmusic |url-status=live}}</ref> In 2011, SanDisk offered various collections of 1000 songs on a single slotMusic card for about $40,<ref>{{cite web|url=http://www.sandisk.com/consumer-products/slotradio|title=slotRadio|publisher=SanDisk|access-date=2011-11-27|archive-date=2011-11-24|archive-url=https://web.archive.org/web/20111124105916/http://www.sandisk.com/consumer-products/slotradio|url-status=live}}</ref> now restricted to compatible devices and without the ability to copy the files.
* '''Integrated USB connector''' – Several companies produce SD cards with built-in [[USB]] connectors allowing them to be accessed by a computer without a card reader.<ref>{{Citation |url=https://www.theregister.co.uk/2005/07/25/review_sandisk_ultra_ii_sd_plus/ |title=SanDisk Ultra II SD Plus USB/SD card |newspaper=The Register |place=[[United Kingdom|UK]] |date=2005-07-25 |access-date=2024-09-11 |archive-date=2019-08-08 |archive-url=https://web.archive.org/web/20190808091122/https://www.theregister.co.uk/2005/07/25/review_sandisk_ultra_ii_sd_plus/ |url-status=live}}</ref>
* '''Integrated display''' – In 2006, ADATA announced a '''Super Info SD''' card with a digital display that provided a two-character label and showed the amount of unused memory on the card.<ref>{{cite web |url=http://www.techpowerup.com/reviews/AData/ADATASuperInfoSD/ |title=A-DATA Super Info SD Card 512&nbsp;MB |publisher=Tech power up |date=2007-02-20 |access-date=2011-12-30 |archive-date=2012-05-18 |archive-url=https://web.archive.org/web/20120518161342/http://www.techpowerup.com/reviews/AData/ADATASuperInfoSD/ |url-status=live}}</ref>

=== SDIO cards ===
[[File:SDIO Vector.svg|thumb|upright=0.65|Secure Digital Input Output (SDIO) mark]]
[[File:HP PhotoSmart SDIO Kamera (cropped).jpg|thumb|upright|Camera using the SDIO interface to connect to some HP [[iPAQ]] devices]]

SDIO (Secure Digital Input Output) is an extension of the SD specification that supports [[input/output]] (I/O) devices in addition to data storage.<ref>{{cite web |url=https://uditagarwal.in/understanding-sd-sdio-and-mmc-interface/ |title=Understanding SD, SDIO and MMC Interface |access-date=2025-06-19}}</ref> SDIO cards are physically and electrically identical to standard SD cards but require compatible host devices with appropriate drivers to utilize their I/O functions. Common examples included adapters for [[GPS]], [[Wi-Fi]], [[digital camera|cameras]], [[barcode reader]]s, and [[modem]]s.<ref>{{cite web |url=https://www.sdcard.org/developers/sd-standard-overview/sdio-isdio/ |title=SDIO / iSDIO Specification Overview |publisher=SD Association |access-date=2025-06-19}}</ref> SDIO was not widely adopted.

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

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

{| class="wikitable" style="text-align:center;font-size:85%"
|+ SD compatibility table
! {{Diagonal split header 2|Slot|Card}}
! scope="col" | SDSC
! scope="col" | SDHC
! scope="col" | SDHC<br />UHS
! scope="col" | SDXC
! scope="col" | SDXC<br />UHS
! scope="col" | SDIO
|-
! style="text-align:left;" | SDSC
| {{Partial}}{{Efn|name=sdsccompat|See [[#Storage capacity and compatibilities|discussion about storage capacity and compatibilities]].}} || {{Partial|FAT16, < 4&nbsp;GB}}{{Efn|name=sdsccompat}} || {{Partial|FAT16, < 4&nbsp;GB}}{{Efn|name=sdsccompat}} || {{No}} || {{No}} || {{No}}
|-
! style="text-align:left;" | SDHC
| {{Yes}} || {{Yes}} || {{good|In non-UHS mode}} || {{Partial|FAT32}} || {{Partial|FAT32 in non-UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDHC UHS
| {{good|In non-UHS mode}} || {{good|In non-UHS mode}} || {{Yes|In UHS mode}} || {{Partial|FAT32 in non-UHS mode}} || {{Partial|FAT32 in UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDXC
| {{Yes}} || {{Yes}} || {{good|In non-UHS mode}} || {{Yes}} || {{good|In non-UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDXC UHS
| {{good|In non-UHS mode}} || {{good|In non-UHS mode}} || {{Yes|In UHS mode}} || {{good|In non-UHS mode}}|| {{Yes|In UHS mode}} || {{No}}
|-
! style="text-align:left;" | SDIO
| {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{partial|Varies}} || {{Yes}}
|}

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

=== Mobile phones ===
[[File:Samsung Galaxy A02s microSD slot.JPG|thumb|A microSD card in a smartphone tray]]

microSD cards are widely used in mobile phones to expand storage, offering offline, low-latency access that benefits tasks like photography, video recording, and file transfers, especially in areas with limited connectivity or costly data plans.<ref>{{cite web |url=https://www.pcmag.com/picks/the-best-microsd-cards |title=The Best microSD Cards for 2024 |website=PCMag |date=2024-12-15 |access-date=2025-06-20}}</ref> Data on removable cards can also be preserved independently of device failure, aiding recovery.

Support for microSD is prevalent in Android smartphones.<ref>{{cite web |url=https://www.androidcentral.com/inside-marshmallow-adoptable-storage |title=Inside Marshmallow: Adoptable Storage |website=Android Central |date=2015-11-15 |access-date=2025-06-20}}</ref> In contrast, Apple has never included microSD card slots in the iPhone, relying solely on built-in flash storage and cloud services.<ref>{{cite web |url=https://www.sdcard.org/press/thoughtleadership/microsd-memory-cards-and-their-importance-with-smartphones/ |title=microSD memory cards and their importance with smartphones |website=SD Association |date=2023-05-24 |access-date=2025-06-20}}</ref>

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

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

=== Personal computers ===
Although many [[personal computer]]s accommodate SD cards as an auxiliary storage device using a built-in slot, or can accommodate SD cards by means of a USB adapter, SD cards cannot be used as the primary [[hard disk]] through the onboard ATA controller, because none of the SD card variants support ATA signalling. Primary [[hard disk]] use requires a separate SD host controller<ref>{{cite web |url=http://www.embeddedarm.com/products/board-detail.php?product=TS-7800 |title=TS-7800 Embedded |publisher=Embeddedarm.com |access-date=2010-08-22 |archive-date=2015-02-15 |archive-url=https://web.archive.org/web/20150215021402/http://www.embeddedarm.com/products/board-detail.php?product=TS-7800 |url-status=dead }}</ref> and firmware support for booting from a SD card (which is typical rather for newer systems and [[Tablet PC|Tablet PCs]] or an SD-to-[[CompactFlash]]{{Efn|CompactFlash uses electrical interface which is compatible with [[parallel ATA]] hard disk drive interface. Firmware of the machine booting from such card is not required to implement CompactFlash boot support explicitly.}} 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.{{Efn|Some SD-to-USB adapters (card readers) do not fully implement [[USB mass storage device class]] or require special drivers. In these cases, boot using such reader may be impossible.}}

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

Since late 2009, newer [[Apple Inc.|Apple]] computers with installed SD card readers have been able to boot in [[macOS]] from SD storage devices, when properly formatted to [[HFS Plus|Mac OS Extended]] file format and the default partition table set to [[GUID Partition Table]].<ref name="Apple Inc. 2011" />

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

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

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

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

More recently (in 2020), the 8-pin interface of microSD has been adapted for use on [[printed circuit board]]s as a [[surface-mount device|surface-mount]]ed (soldered) [[integrated circuit]] chip in standard LGA8 or WSON8 packaging, measuring {{cvt|8|x|6|x|1|mm|frac=64}}. Such a chip is called an ''{{vanchor|SD NAND}}''. The microSD interface offers several benefits compared to more established NAND formats: the small number of pins makes it easier to route the connections (unlike eMMC and raw NAND) and the card itself handles details such as wear leveling (unlike raw NAND).<ref>{{cite web |title=New Part Day: SD NAND Are Surface Mount Chips That Work Like An SD Card |url=https://hackaday.com/2020/12/29/new-part-day-sd-nand-are-surface-mount-chips-that-work-like-an-sd-card/ |website=Hackaday |date=29 December 2020}}</ref> They can alternatively be viewed as ''SPI NAND'' or ''SPI Flash'' units (which came in a similar packaging but only supported the SPI bus) with added SD bus (1-bit and 4-bit) capability and support for the SD command set.

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

=== Counterfeits ===
Commonly found on the market are mislabeled or counterfeit Secure Digital cards that report a fake capacity or run slower than labeled.<ref>{{cite web |last=bunnie |title=On MicroSD Problems |url=https://www.bunniestudios.com/blog/?page_id=1022 |access-date=2024-01-22 |website=bunniestudios.com |archive-date=2024-09-11 |archive-url=https://web.archive.org/web/20240911013533/https://www.bunniestudios.com/blog/on-microsd-problems/ |url-status=live }}</ref><ref>{{cite web |last=Schnurer |first=Georg |title=Gefälschte SD-Karten |language=de |trans-title=Fake SD-cards |publisher=Heise mobile – c't magazin für computertechnik |date=2007-02-28 |url=http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |access-date=2013-06-07 |archive-date=2013-06-23 |archive-url=https://web.archive.org/web/20130623055703/http://www.heise.de/mobil/meldung/Gefaelschte-SD-Karten-151283.html |url-status=dead }}</ref><ref>{{cite web |url=http://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |title=Smartphones wählerisch bei microSDHC-Karten |publisher=Heise mobile – c't magazin für computertechnik |date=2013-03-18 |access-date=2013-06-09 |last=Feddern |first=Boi |language=de |archive-date=2019-01-01 |archive-url=https://web.archive.org/web/20190101010525/https://www.heise.de/mobil/meldung/Smartphones-waehlerisch-bei-microSDHC-Karten-1825259.html |url-status=live }}</ref> Software tools exist to check and detect [[USB flash drive#Counterfeit products|counterfeit products]],<ref>{{cite web |title=H2testw heise Download |language=de |url=https://www.heise.de/download/product/h2testw-50539 |access-date=2016-11-26 |archive-date=2016-11-26 |archive-url=https://web.archive.org/web/20161126111115/https://www.heise.de/download/product/h2testw-50539 |url-status=live}}</ref><ref>{{cite web |title=F3 by Digirati |url=https://oss.digirati.com.br/f3/ |access-date=2016-11-26 |archive-date=2016-11-24 |archive-url=https://web.archive.org/web/20161124080508/http://oss.digirati.com.br/f3/ |url-status=live}}</ref><ref>{{cite web |url=https://www.usbdev.ru/articles/detect_controller/ |language=ru |title=Определение модели контроллера и памяти флешки |date=20 February 2013 |trans-title=Detecting controller model and memory type of flash drive |publisher=usbdev.ru |access-date=2018-01-06 |archive-date=2023-06-24 |archive-url=https://web.archive.org/web/20230624000054/https://www.usbdev.ru/articles/detect_controller/ |url-status=live }}</ref> and in some cases it is possible to repair these devices to remove the false capacity information and use its real storage limit.<ref>[http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ "About VID PID Repairing Counterfeit Flash Drives – Steps To Succeed"] {{Webarchive|url=https://web.archive.org/web/20110109230403/http://fixfakeflash.wordpress.com/2008/12/11/about-vid-pid-repairing-counterfeit-flash-drives-steps-to-succeed/ |date=2011-01-09 }}, fixfakeflash.wordpress.com, retrieved November 16, 2010</ref>

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

<gallery widths="220px" heights="165px">
File:Samsung Pro 64gb micro-SDXC original and falsification front and back.jpg|Genuine [[Samsung Electronics|Samsung]] microSD (left) and counterfeit (right). The counterfeit claims to have 64&nbsp;GB of capacity, but when trying to write more than 8&nbsp;GB, [[data loss]] occurs.
File:Decapsulated microSD memory card lineup-genuine, questionable, and fake-counterfeit.jpg|Images of genuine, questionable, and counterfeit microSD cards before and after decapsulation. Details at [http://www.bunniestudios.com/blog/?page_id=1022 source].
</gallery>

== Technical details ==

=== Physical size ===
[[File:MicroSD MemoryCard 002.jpg|thumb|upright|Size comparison of families: SD (blue), miniSD (green), microSD (red)]]

The SD card specification defines three physical sizes. The SD and SDHC families are available in all three sizes, but the SDXC and SDUC families are not available in the mini size, and the SDIO family is not available in the micro size. Smaller cards are usable in larger slots through use of a passive adapter.

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

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

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

The physical interface comprises 9 pins, except that the miniSD card adds two unconnected pins in the center and the microSD card omits one of the two V<sub>SS</sub> (Ground) pins.<ref name="Specification 4.10" />

[[File:MMC-SD-miniSD-microSD-Color-Numbers-Names.gif|thumb|upright|Official pin numbers for 4 card types (top to bottom): [[MultiMediaCard|MMC]], SD, miniSD, microSD. This shows the evolution from the older MMC, on which SD is based. Note: This drawing does not show 8 new UHS-II contacts that were added in spec 4.0.]]

{| class="wikitable" style="text-align:center;font-size:85%"
|+ SPI bus mode<ref name="Specification 9.00" />
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| 1 ||1 ||1 ||2 ||nCS ||I ||PP ||style="text-align:left"|SPI Card Select [CS] (Negative logic)
|-
| 2 ||2 ||2 ||3 ||DI ||I ||PP ||style="text-align:left"|SPI Serial Data In [MOSI]
|-
| 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|SPI Serial Clock [SCLK]
|-
| 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 7 ||7 ||7 ||7 ||DO ||O ||PP ||style="text-align:left"|SPI Serial Data Out [MISO]
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative logic)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

{| class="wikitable" style="text-align:center;font-size:85%"
|+ One-bit SD bus mode<ref name="Specification 9.00" />
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| 1 ||1 ||1 ||2 ||CD ||I/O ||. ||style="text-align:left"|Card detection (by host) and<br />non-SPI mode detection (by card)
|-
| 2 ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response
|-
| 3 ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 4 ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| 5 ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock
|-
| 6 ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| 7 ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||NC<br />nIRQ ||.<br />O ||.<br />OD ||style="text-align:left"|Unused (memory cards)<br />Interrupt (SDIO cards) (negative Logic)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||NC ||. ||. ||style="text-align:left"|Unused
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

{| class="wikitable" style="text-align:center;font-size:85%"
|+ Four-bit SD bus mode<ref name="Specification 9.00" />
|-
! [[MultiMediaCard|MMC]]<br />pin !! SD<br />pin !! miniSD<br />pin !! microSD<br />pin !! Name !! I/O !! Logic !! Description
|-
| . ||1 ||1 ||2 ||DAT3 ||I/O ||PP ||style="text-align:left"|SD Serial Data 3
|-
| . ||2 ||2 ||3 ||CMD ||I/O ||PP,<br />OD ||style="text-align:left"|Command,<br />Response
|-
| . ||3 ||3 ||style="background: gray" | {{sp}} ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| . ||4 ||4 ||4 ||VDD ||S ||S ||style="text-align:left"|Power
|-
| . ||5 ||5 ||5 ||CLK ||I ||PP ||style="text-align:left"|Serial clock
|-
| . ||6 ||6 ||6 ||VSS ||S ||S ||style="text-align:left"|Ground
|-
| . ||7 ||7 ||7 ||DAT0 ||I/O ||PP ||style="text-align:left"|SD Serial Data 0
|-
| style="background: gray" | {{sp}} ||8 ||8 ||8 ||DAT1<br />nIRQ ||I/O<br />O ||PP<br />OD ||style="text-align:left"|SD Serial Data 1 (memory cards)<br />Interrupt Period (SDIO cards share pin via protocol)
|-
| style="background: gray" | {{sp}} ||9 ||9 ||1 ||DAT2 ||I/O ||PP ||style="text-align:left"|SD Serial Data 2
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||10 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|-
| style="background: gray" | {{sp}} ||style="background: gray" | {{sp}} ||11 ||style="background: gray" | {{sp}} ||NC ||. ||. ||style="text-align:left"|Reserved
|}

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

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

==== Command interface ====
SD cards and host devices initially communicate through a [[synchronous]] one-bit interface, where the host device provides a clock signal that strobes single bits in and out of the SD card. The host device thereby sends 48-bit commands and receives responses. The card can signal that a response will be delayed, but the host device can abort the dialogue.<ref name="Specification 3.01" />

Through issuing various commands, the host device can:<ref name="Specification 3.01" />
* Determine the type, memory capacity and capabilities of the SD card
* Command the card to use a different voltage, different clock speed, or advanced electrical interface
* Prepare the card to receive a block to write to the flash memory, or read and reply with the contents of a specified block.

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

==== Electrical interface ====
All SD card families initially use a 3.3&nbsp;[[volt]] electrical interface. On command, SDHC and SDXC cards can switch to 1.8&nbsp;V operation.<ref name="Specification 3.01" />

At power-up or card insertion, the voltage on pin 1 selects either the Serial Peripheral Interface (SPI) bus or the SD bus. The SD bus starts in one-bit mode, but the host device may issue a command to switch to the four-bit mode, if the SD card supports it. For various card types, support for the four-bit SD bus is either optional or mandatory.<ref name="Specification 3.01" />

After determining that the SD card supports it, the host device can also command the SD card to switch to a [[#Speed|higher transfer speed]]. Until determining the card's capabilities, the host device should not use a clock speed faster than 400&nbsp;kHz. SD cards other than SDIO (see below) have a "Default Speed" clock rate of 25&nbsp;MHz. The host device is not required to use the maximum clock speed that the card supports. It may operate at less than the maximum clock speed to conserve power.<ref name="Specification 3.01" /> Between commands, the host device can stop the clock entirely.

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

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

On such SD cards, standard utility programs such as Mac OS X's "{{Nowrap|[[Disk Utility]]}}" or Windows' [[SCANDISK]] can be used to repair a corrupted filing system and sometimes recover deleted files. [[Defragmentation]] tools for FAT file systems may be used on such cards. The resulting consolidation of files may provide a marginal improvement in the time required to read or write the file,<ref>{{Citation | url = https://www.sdcard.org/developers/overview/speed_class/ | title = Fragmentation and Speed | date = 11 December 2020 | publisher = SD Card | access-date = 21 November 2011 | archive-date = 3 June 2018 | archive-url = https://web.archive.org/web/20180603051813/https://www.sdcard.org/developers/overview/speed_class/ | url-status = live }}</ref> but not an improvement comparable to defragmentation of hard drives, where storing a file in multiple fragments requires additional physical and relatively slow, movement of a drive head.<ref>{{Cite web |date=2022-06-14 |title=What does defragmenting do for an SSD? |url=https://www.crucial.com/articles/about-ssd/should-you-defrag-an-ssd?srsltid=AfmBOooR-a3P674anTsYjazYPNT1TIdawKE_1bh5uhYbNxFJ9i6sW |url-status=live |access-date=2025-11-03 |website=www.crucial.com}}</ref> Moreover, defragmentation performs writes to the SD card that count against the card's rated lifespan. The write endurance of the physical memory is discussed in the article on [[Flash memory degradation|flash memory]]; newer technology to increase the storage capacity of a card provides worse write endurance.{{citation needed|date=September 2023}}

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

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

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

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

=== Power consumption ===
The power consumption of SD cards varies by its speed mode, manufacturer and model.<ref>{{Cite web |date=2020-05-01 |title=SD Express and microSD Express Cards: The Best Choice for Your Future Product Designs |url=https://www.sdcard.org/pdf/SD_Express_microSD_Express_BestChoice_WhitePaper20200515.pdf |url-status=live |access-date=2025-11-03 |website=www.sdcard.org}}</ref>

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

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

{| class="wikitable" style="text-align:center;font-size:85%"
|+ Card requirements in different bus speed modes<ref name="Specification 9.00" />
|-
! Bus speed<br />mode !! Max. bus<br />speed<br />[MB/s] !! Max. clock<br />frequency<br />[MHz] !! Signal<br />voltage<br />[V] !! SDSC<br />[W] !! SDHC<br />[W] !! SDXC<br />[W]
|-
| HD312 || 312 || 52 || 0.4 || – || 2.88 || 2.88
|-
| FD156 || 156 || 52 || 0.4 || – || 2.88 || 2.88
|-
| SDR104 || 104 || 208 || 1.8 || – || 2.88 || 2.88
|-
| SDR50 || 50 || 100 || 1.8 || – || 1.44 || 1.44
|-
| DDR50 || 50 || 50 || 1.8 || – || 1.44 || 1.44
|-
| SDR25 || 25 || 50 || 1.8 || – || 0.72 || 0.72
|-
| SDR12 || 12.5 || 25 || 1.8 || – || 0.36 || 0.36 / 0.54
|-
| High Speed || 25 || 50 || 3.3 || 0.72 || 0.72 || 0.72
|-
| Default Speed || 12.5 || 25 || 3.3 || 0.33 || 0.36 || 0.36 / 0.54
|}

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

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

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

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

Version 1.01 let an SDSC card use a 4-bit field to indicate 1,024 or 2,048 bytes per block instead.<ref name="Specification 3.01" /> Doing so enabled cards with 2&nbsp;GB and 4&nbsp;GB capacity, such as the Transcend 4&nbsp;GB SD card, the Memorette 4&nbsp;GB SD card and the Hoco 4&nbsp;GB microSD card.{{citation needed|date=September 2023}}

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

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

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

Later versions state (at Section 4.3.2) that a 2&nbsp;GB SDSC card shall set its READ_BL_LEN (and WRITE_BL_LEN) to indicate 1,024 bytes, so that the above computation correctly reports the card's capacity, but that, for consistency, the host device shall not request (by CMD16) block lengths over 512&nbsp;B.<ref name="Specification 3.01" />

==== Versions 2 and 3 ====
In the definition of SDHC cards in version 2.0, the C_SIZE portion of the CSD is 22 bits and it indicates the memory size in multiples of 512&nbsp;KB (the C_SIZE_MULT field is removed and READ_BL_LEN is no longer used to compute capacity). Two bits that were formerly reserved now identify the card family: 0 is SDSC; 1 is SDHC or SDXC; 2 and 3 are reserved.<ref name="Specification 3.01" /> Because of these redefinitions, older host devices do not correctly identify SDHC or SDXC cards nor their correct capacity.
* SDHC cards are restricted to reporting a capacity not over 32&nbsp;GB.{{citation needed|date=September 2023}}
* SDXC cards are allowed to use all 22 bits of the C_SIZE field. An SDHC card that did so (reported C_SIZE > 65,375 to indicate a capacity of over 32&nbsp;GB) would violate the specification. A host device that relied on C_SIZE rather than the specification to determine the card's maximum capacity might support such a card, but the card might fail in other SDHC-compatible host devices.{{citation needed|date=September 2023}}

Capacity is calculated thus:

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

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

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

== Adapters ==
Various passive adapters are available to allow smaller SD cards to work in larger SD card slots.
<gallery widths="220" heights="165">
File:MicroSD to SD adapter, disassembled.png|Dismantled microSD to SD adapter showing the passive connection from the microSD card slot on the bottom to the SD pins on the top
File:Sdadaptersandcards.jpg|MicroSD-to-SD adapter (left), microSD-to-miniSD adapter (middle), microSD card (right)
File:MiniSD memory card including adapter.jpg|MiniSD memory card including adapter
File:SD card adapters.jpg|microSD card (left), microSD to SD card adapter (right)
File:SD card adapter.jpg|microSD card inserted into microSD to SD card adapter
File:XD cards, the MASD-1 microSD card attachment and a microSD card.jpg|In 2008 Olympus started bundling microSD card to xD-Picture Card adapters with their digital cameras
</gallery>

== Openness of specification ==
The SD format was introduced in August 1999.<ref name="DP Review 1999" /> Like most memory card formats, SD is covered by [[patent]]s and [[trademark]]s. [[Royalty payment|Royalties]] apply to the manufacture and sale of SD cards and host adapters, with the exception of SDIO devices. As of 2025, the SD Association (SDA) charged annual membership fees of US$2,500 for general members and US$4,500 for executive members.<ref>{{cite web |title=Join the SD Association |url=https://www.sdcard.org/join/ |publisher=SD Association |archive-url=https://web.archive.org/web/20250615002737/https://www.sdcard.org/join/ |archive-date=June 15, 2025 |url-status=live}}</ref>

Early versions of the SD specification were only available under a [[non-disclosure agreement]] (NDA), which restricted the development of [[open-source software|open-source]] drivers. Despite these limitations, developers reverse-engineered the interface and created free software drivers for SD cards that did not use digital rights management (DRM).<ref>{{cite web |url=http://www.linux.com/archive/feed/20060 |title=Sharp Linux PDA promotes the use of proprietary SD card, but more open MMC works just fine |date=14 June 2007 |publisher=Linux.com |access-date=2010-08-22 |archive-date=2010-12-15 |archive-url=https://web.archive.org/web/20101215172756/http://www.linux.com/archive/feed/20060 |url-status=live }}</ref>

In 2006, the SDA began publishing a "Simplified Specification" under a less restrictive license.  It includes documentation for the physical layer, SDIO, and certain extensions, allowing broader implementation without requiring an NDA or paid membership.<ref>[http://www.sdcard.org/developers/tech/sdcard/pls/ Simplified Specification Agreement] {{webarchive |url=https://web.archive.org/web/20081028165644/http://www.sdcard.org/developers/tech/sdcard/pls/ |date=2008-10-28}}</ref><ref>{{Cite web |url=https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |title=Simplified Specification|accessdate=July 31, 2024 |archive-date=December 18, 2020|archive-url=https://web.archive.org/web/20201218104400/https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |url-status=live}}</ref>

== Revisions ==
{| class="wikitable"
|+ History of SD specification versions
! {{Abbr|Ver.|Version}}
! Year
! Notable changes
! {{Reference column heading}}
|-
| 1.00
| 2000
| Preliminary specification
| {{N/A}}
|-
| 1.01
| 2001
| Minor updates
| <ref name="Specification 1.01" />
|-
| 1.10
| rowspan="2" | 2006
| Official initial release
| <ref name="Specification 1.10" />
|-
| 2.00
| Added SDHC and Speed Classes C2, C4, and C6<ref>{{cite web |title=SD Specification Part 1 Physical Layer Simplified Specification Version 2.00 |url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_200.pdf |archive-url=https://web.archive.org/web/20250101000000/https://www.sdcard.org/downloads/pls/simplified_specs/part1_200.pdf |archive-date=2025-01-01 |access-date=2025-06-19 |publisher=SD Association}}</ref>
| <ref name="Specification 2.00" />
|-
| 3.01
| 2010
| Added SDXC, UHS-I bus and Speed Class C10/UHS Speed Class U1
| <ref name="Specification 3.01" />
|-
| 4.10
| 2013
| Added UHS-II bus, UHS Speed Class U3, and enhanced power and function support
| <ref name="Specification 4.10" />
|-
| 5.00
| rowspan="2" | 2016
| Added Video Speed Classes V6, V10, V30, V60, and V90
| <ref name="Specification 5.00" />
|-
| 5.10
| Added Application Performance Class A1
| <ref name="Pinto 2017" />
|-
| 6.00
| 2017
| Added Application Performance Class A2 (with command queuing and write caching) and Card Ownership Protection
| <ref name="Specification 6.00" />
|-
| 7.10
| rowspan="2" | 2020
| Added SD Express, microSD Express, SDUC, and made CPRM optional
| <ref name="Specification 7.10" />
|-
| 8.00
| Added PCIe 4.0, added dual-lane PCIe on full-size cards
| <ref name="Specification 8.00" />
|-
| 9.00
| 2022
| Introduced new security features and enhanced write protection
| <ref name="Specification 9.00" />
|-
| 9.10
| 2023
| Added SD Express Speed Classes E150, E300, E450, and E600
| <ref name="Specification 9.10" />
|}

== See also ==
[[File:Flash memory cards size.jpg|thumb|Size comparison of various flash cards: SD, [[CompactFlash]], [[MultiMediaCard|MMC]], [[xD-Picture Card|xD]]]]
* [[Comparison of memory cards]]
* [[Microdrive]]
* [[Universal Flash Storage]]

== Footnotes ==
{{Notelist}}

== References ==
{{Reflist|refs=

<ref name="Specification 1.01">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 1.01'' |date=April 15, 2001 |publisher=SD Association |url=https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver1.01.pdf |archive-url=https://web.archive.org/web/20250615054350/https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver1.01.pdf |archive-date=June 15, 2025 |url-status=live}}</ref>

<ref name="Specification 1.10">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 1.10'' |date=April 3, 2006 |publisher=SD Association |url=https://users.ece.utexas.edu/~valvano/EE345M/SD_Physical_Layer_Spec.pdf |archive-url=https://web.archive.org/web/20250614232848/https://d1.amobbs.com/bbs_upload782111/files_8/ourdev_182740.pdf |archive-date=June 14, 2025 |url-status=dead}}</ref>

<ref name="Specification 2.00">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 2.00'' |date=September 25, 2006 |publisher=SD Association |url=https://users.ece.utexas.edu/~valvano/EE345M/SD_Physical_Layer_Spec.pdf |archive-url=https://web.archive.org/web/20250614230843/https://users.ece.utexas.edu/~valvano/EE345M/SD_Physical_Layer_Spec.pdf |archive-date=June 14, 2025 |url-status=dead}}</ref>

<ref name="Specification 3.01">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 3.01'' |date=May 18, 2010 |publisher=SD Association |url=http://www.sdcard.org/downloads/pls/simplified_specs/archive/part1_301.pdf |archive-url=https://web.archive.org/web/20131205014133/https://www.sdcard.org/downloads/pls/simplified_specs/archive/part1_301.pdf |archive-date=December 5, 2013 |url-status=dead}}</ref>

<ref name="Specification 4.10">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 4.10'' |date=January 22, 2013 |publisher=SD Association |url=https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |archive-url=https://web.archive.org/web/20150905093128/https://www.sdcard.org/downloads/pls/simplified_specs/part1_410.pdf |archive-date=September 5, 2015 |url-status=dead}}</ref>

<ref name="Specification 5.00">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 5.00'' |date=August 10, 2016 |publisher=SD Association |url=https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver5.10.pdf |archive-url=https://web.archive.org/web/20250615041919/https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver5.10.pdf |archive-date=June 15, 2025 |url-status=live}}</ref>

<ref name="Specification 6.00">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 6.00'' |date=April 10, 2017 |publisher=SD Association |url=https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |archive-url=https://web.archive.org/web/20250406192428/https://www.taterli.com/wp-content/uploads/2017/05/Physical-Layer-Simplified-SpecificationV6.0.pdf |archive-date=April 6, 2025 |url-status=dead}}</ref>

<ref name="Specification 7.10">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 7.10'' |date=March 25, 2020 |publisher=SD Association |url=https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver7.10.pdf |archive-url=https://web.archive.org/web/20250615044605/https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver7.10.pdf |archive-date=June 15, 2025 |url-status=live}}</ref>

<ref name="Specification 8.00">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 8.00'' |date=September 23, 2020 |publisher=SD Association |url=https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver8.00.pdf |archive-url=https://web.archive.org/web/20250615045554/https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver8.00.pdf |archive-date=June 15, 2025 |url-status=live}}</ref>

<ref name="Specification 9.00">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 9.00'' |date=August 22, 2022 |publisher=SD Association |url=https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver9.00.pdf |archive-url=https://web.archive.org/web/20250615054831/https://www.sdcard.org/cms/wp-content/themes/sdcard-org/dl.php?f=Part1_Physical_Layer_Simplified_Specification_Ver9.00.pdf |archive-date=June 15, 2025 |url-status=live}}</ref>

<ref name="Specification 9.10">{{cite web |title=''SD Part 1, Physical Layer Simplified Specification, Version 9.10'' |date=December 1, 2023 |publisher=SD Association |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}}</ref>

}}<!--End of Reflist template-->

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

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

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