Nintendo DS storage devices are some of the devices used to store a licensed developer's work-in-progress images, homebrew video games, or downloaded commercial games, since the Nintendo DS is not sold with a rewritable storage medium. (Licensed developers can use the blue Intelligent Systems Nitro Emulator box to flash cards.) There are two main classes of storage devices: older devices that fit in SLOT-2 (the Game Boy Advance Game Pak slot) and newer devices that fit in SLOT-1 (the DS Game Card slot). SLOT-2, or 1st generation, devices have historically been cheaper due to economies of scale inherited from their use with Game Boy Advance homebrew but require a booting tool in SLOT-1 in order to use the touch screen and other DS features. Devices that only use SLOT-1, or 2nd generation, do not work with GBA homebrew, but as of 2007[update], they are becoming easier to use and less expensive, rivaling many SLOT-2 devices in price which may have been cheaper.
First generation devices include GBA flash cartridges, GBAMP CF, SuperCard and M3. Second generation devices include R4 Revolution, CycloDS, G6 Real, and DS-X. The storage device either contains flash memory or a slot for a memory card to store homebrew. Storage devices with a memory card slot usually have a larger storage capacity than flash memory devices. Although flash memory capacity is usually measured in megabits (Mbit), memory card capacity is usually measured in megabytes (MB). (8 Mbit = 1 MB)
Different brands of storage device differ in their support for homebrew, support for DS and Game Boy Advance ROMs, special features, such as playing media files, physical size and cost. Strictly speaking, a storage device is not necessary for DS with FlashMe installed because homebrew can be sent to the DS using WMB. However, this is not a very portable method because the DS needs to be within range of a suitable Wi-Fi card.