An SD card is about the size of a postage stamp and weighs approximately two grams. It is similar in size to a MultiMediaCard, but smaller than older memory card types such as the SmartMedia card and the CompactFlash card. Both MMC and SD cards provide encryption capabilities for protected content to ensure secure distribution of copyrighted material, such as digital music, video, and e-books. SD cards are available with storage capacities as high as 4 gigabytes.
The SD card was jointly developed by Matsushita, SanDisk, and Toshiba.