Definition: CompactFlash (CF) is a type of flash memory card used in digital cameras to store data about images. CF cards are available in two configurations: Type I and Type II. Type I cards are slightly thinner than Type II cards. If a digital camera has a CF Type I slot, it cannot use Type II memory cards. However, digital cameras with CF Type II slots can read both types of CF cards.

CF cards larger than 2GB (gigabytes) in capacity use a slightly different storage technology than CF cards at 2GB and smaller capacities.

Some digital cameras that use CF cards cannot read CF cards with more than 2GB of storage capacity because of the change in storage technology.

SanDisk developed the first CF cards in 1994. CF cards are some of the largest memory cards, and they're almost square in shape. CF cards measure 43 mm by 36 mm (1.69 x 1.42 inches). Type I cards measure 3.3 mm in thickness (0.13 inches), while Type II cards measure 5 mm in thickness (0.20 inches).