The SD card is a proprietary, non-risky, Memory Wave System flash memory card format developed by the SD Association (SDA). They are available three bodily forms: the total-dimension SD, the smaller miniSD (now out of date), and the smallest, microSD. Owing to their compact kind factor, SD playing cards have been extensively adopted in a variety of portable shopper electronics, together with digital cameras, camcorders, video game consoles, cell phones, motion cameras, and digital camera drones. The format was launched in August 1999 as Safe Digital by SanDisk, Panasonic (then often known as Matsushita), and Kioxia (then a part of Toshiba). It was designed as a successor to the MultiMediaCard (MMC) format, introducing several enhancements including a digital rights administration (DRM) feature, a extra durable physical casing, and a mechanical write-protect switch. These enhancements, combined with strong business support, contributed to its widespread adoption. To manage licensing and mental property rights, the founding companies established SD-3C, LLC. In January 2000, in addition they formed the SD Affiliation, a non-profit group responsible for growing the SD specifications and selling the format.

As of 2023, the SDA includes roughly 1,000 member companies. The association makes use of trademarked logos owned by SD-3C to implement compliance with official standards and to point product compatibility. In 1994, SanDisk introduced the CompactFlash (CF) format, one among the first profitable flash memory card types. CF outpaced a number of competing early formats, including the Miniature Card and SmartMedia. However, the late nineties saw a proliferation of proprietary formats equivalent to Sony's Memory Stick and the xD-Picture Card from Olympus and Fujifilm, leading to a fragmented Memory Wave System card market. To address these challenges, SanDisk partnered with Siemens and Nokia in 1996 to develop a new postage stamp-sized Memory Wave card called the MultiMediaCard (MMC). Whereas technically revolutionary, MMC adoption was slow, and even Nokia was sluggish to integrate support for it into its cell units. In 1999, SanDisk was approached by Panasonic (then referred to as Matsushita) and Kioxia (then a part of Toshiba) to develop a brand new format as a second-generation successor to MMC.

The objective was to create a portable, high-performance memory card with built-in safety features and broader interoperability. Involved about shedding market share to Sony's proprietary Memory Stick, Toshiba and Panasonic saw the collaboration as a chance to establish an open, trade-backed customary. Panasonic and Toshiba, who had beforehand collaborated on the Tremendous Density Disc (a DVD precursor), reused its stylized "SD" brand for the Secure Digital (SD) card format. Anticipating the growth of MP3 players, they also advocated for digital rights management (DRM) help in search of to reassure content publishers cautious of piracy. The DRM system adopted-Content material 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. Though typically cited as an element in the format's broad trade support, CPRM was rarely carried out in practice. SD cards also featured a mechanical write-protect swap, and early SD slots maintained backward compatibility with MMC playing cards. Based on SanDisk, consumer adoption was accelerated by Toshiba and Panasonic's dedication to launching suitable gadgets in parallel with the playing cards.

To help standardization and interoperability, SanDisk, Toshiba, and Panasonic introduced the creation of the SD Affiliation (SDA) on the January 2000 Shopper Electronics Show (CES). Headquartered in San Ramon, California, Memory Wave the SDA initially included 30 member firms and has since grown to encompass round 800 organizations worldwide. On the March 2003 CeBIT commerce present, SanDisk launched and demonstrated the miniSD card format. The SD Affiliation (SDA) adopted miniSD later that year as a small-kind-issue extension to the SD card customary, intended primarily for use in cellphones. Nonetheless, the format was largely phased out by 2008 following the introduction of the even smaller microSD card. TransFlash identify remains in common use as a generic term for microSD playing cards. A passive adapter allows microSD cards to be used in customary SD card slots, maintaining backward compatibility across devices. The storage capacity of SD playing cards increased steadily all through the 2010s, driven by advances in NAND flash manufacturing and interface speeds. In January 2009, the SDA launched the Safe Digital extended Capacity (SDXC) format, supporting as much as 2 TB of storage and switch speeds as much as 300 MB/s.

SDXC cards are formatted with the exFAT file system by default. The primary SDXC cards appeared in 2010, with early models offering capacities of 32 to 64 GB and browse/write speeds of a number of hundred megabits per second. Consumer adoption accelerated as digital cameras, smartphones, and card readers gained SDXC compatibility. By 2011, manufacturers supplied SDXC playing cards in sixty four and 128 GB capacities, with some fashions supporting UHS Velocity Class 10 and quicker. The Secure Digital Ultra Capability (SDUC) specification, announced in 2018, expanded most capacity to 128 TB and elevated theoretical switch speeds to 985 MB/s. There are four outlined SD capacity standards: Standard Capability (SDSC), High Capability (SDHC), Prolonged Capacity (SDXC), and Ultra Capability (SDUC). In addition to specifying maximum storage limits, these requirements additionally outline preferred file systems for formatting playing cards. The unique Secure Digital (SD) card was launched in 1999 as a successor to the MMC format. The title SD Customary Capability (SDSC) was applied later to distinguish it from newer variants.