The xD (extreme Digital) Picture Card is a flash memory card for digital cameras, MP3 players, and digital voice recorders. The xD cards were initially developed by Fujifilm and Olympus. Available for commercial sale in July 2002, xD cards are still used in many devices mostly competing with the popular formats of the Secure Digital card, CompactFlash, and Sony's Memory Stick.  Although xD has a lower power consumption and significantly smaller size (20 mm × 25 mm × 1.78 mm, 2.0 g) than the aforementioned formats, the limitation of available storage on a single card (no larger than 2 GB) places a disadvantage on the format. 

The standard xD was available in sizes up to 512MB.  The xD type M, released February 2005, is available in sizes up to 2GB, however it has slower read/write speed than the standard card. Released in November of 2005, the type H card has the same maximum capacity of the type M, but has a considerably faster data rate.  Finally, with a stated write speed of 3.75MB/sec, in April 2008 the M+ card was released.  xD cards under the brands of Olympus and Fujifilm are manufactured by Toshiba Corp. and Samsung Electronics.  Kodak, SanDisk, PNY, and Lexar produce their own line of xD cards.