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
From top to bottom: SD, miniSD, microSD
Media typeMemory card
  • 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 sizeVariable
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 mechanismSame as Read
StandardSD Standard
Developed bySD Association
  • 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)
  • Standard: ~2 g
  • Mini: ~800 mg
  • Micro: ~250 mg
UsagePortable devices, such as digital cameras and mobile phones (including most smartphones)
Extended fromMultiMediaCard
ReleasedAugust 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]

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