Memory cards are used to store digitised information generated by a variety of modern devices, including cameras. They are available in a wide range of capacities, speeds, physical sizes and qualities. Capacity and speed seem to increase all the time, although prices decrease at a comparable rate. Even cards with modest specifications can now store thousands of print-quality images in JPEG format.

Memory cards use flash memory, a non-volatile technology requiring no power to retain stored data. This is a key requirement because data must remain secure when a card is removed from a camera.

Choice of card depends in part upon the physical and electronic design of the camera. Some cameras feature slots that accept more than one physical size of memory card, and may have more than one slot, but others accept only cards of particular dimensions. The electronic specifications of camera and card must also clearly be compatible.

However, the range of memory cards available is such that even when physical and electronic compatibility is taken in to account a large choice remains. Factors that separate compatible cards include price, quality and speed.