SD card

Secure Digital, officially abbreviated as SD, is a proprietary non-volatile flash memory card format developed by the SD Association (SDA) for use in portable devices.

Secure Digital
(SD, SDHC, SDXC, SDUC)

From top to bottom: SD, miniSD, microSD
Media type	Memory card
Encoding	Bit
Capacity	SD: Up to 2 GB SDHC: over 2 GB to 32 GB SDXC: over 32 GB to 2 TB SDUC: over 2 TB to 128 TB
Block size	Variable
Read mechanism	Standard: 12.5 MB/s High-speed: 25 MB/s UHS-I: 50 MB/s or 104 MB/s UHS-II: 156 MB/s full-duplex, or 312 MB/s half-duplex UHS-III: 312 MB/s full-duplex, or 624 MB/s half-duplex Express: ≥ 985 MB/s full-duplex
Write mechanism	Same as Read
Standard	SD Standard
Developed by	SD Association
Dimensions	Standard: 32.0×24.0×2.1 mm (1.260×0.945×0.083 in) 1,612.8 mm3 (0.09842 in3) Mini: 21.5×20.0×1.4 mm (0.846×0.787×0.055 in) 602 mm3 (0.0367 in3) Micro: 15.0×11.0×1.0 mm (0.591×0.433×0.039 in) 165 mm3 (0.0101 in3)
Weight	Standard: ~2 g Mini: ~800 mg Micro: ~250 mg
Usage	Portable devices, such as digital cameras and mobile phones (including most smartphones)
Extended from	MultiMediaCard
Released	August 1999

The standard was introduced in August 1999 by joint efforts between SanDisk, Panasonic (Matsushita) and Toshiba as an improvement over MultiMediaCards (MMCs),[1] and has become the industry standard. The three companies formed SD-3C, LLC, a company that licenses and enforces intellectual property rights associated with SD memory cards and SD host and ancillary products.[2]

The companies also formed the SD Association (SDA), a non-profit organization, in January 2000 to promote and create SD Card standards.[3] SDA today has about 1,000 member companies. The SDA uses several trademarked logos owned and licensed by SD-3C to enforce compliance with its specifications and assure users of compatibility.[4]