(
Secure
Digital Memory Card) A family of flash memory cards available in two sizes: SD and microSD. Introduced in 1999 by Panasonic, Toshiba and SanDisk, and managed by the SD Association, the SD card superseded the MultiMediaCard (see
MMC). Capacities have reached 1TB. See
microSD and
flash memory.
The full-size SD cards are widely used for storage in stand-alone digital cameras. The small microSD cards have also been used for storage in various smartphones. However, vendors are increasingly dropping that option, requiring customers to choose the built-in storage they need at the time of purchase.
For video recording, SD cards support various write speeds, and although they were designed for copyright protection (the S in SD means Secure), they were not widely used for security (see
CPRM and
SD card classes). See
Video HD,
Eye-Fi and
SDIO card.
SD Express - More Speed
In 2018, SD Express added support for additional interfaces and higher speeds while keeping backward compatibility (see
SD Express).
microSD - miniSD - SD
The microSD card (left) obsoleted the miniSD format. Adapters let microSDs plug into full-size SD slots (see
microSD).
(Images courtesy of SanDisk Corporation.)
SD Year File
Format Into Capacity System
SD 1999 1-2GB FAT16
SDHC 2006 2-32GB FAT32
SDXC 2009 32GB-2TB exFAT
SDUC 2018 2TB-128TB exFAT
More Speed and Capacity
The newer HC, XC and UC formats added more speed and capacity. All new SD slots accept the older cards as well. See
FAT32 and
exFAT.
(Images courtesy of SanDisk Corporation.)