CompactFlash (or CF) cards are small expansion cards aimed primarily at the mobile technology markets. The CompactFlash standard was first introduced by the CompactFlash Association in 1994.

A typical CompactFlash card will weigh in at half an ounce and are (typically) the size of a matchbook. They provide complete PCMCIA-ATA functionality and compatibility.

There are two subset types and form-factors of CF cards: They are

  • CF Type I
    43mm (1.7") x 36mm (1.4") x 3.3mm (0.13").

  • CF Type II
    43mm (1.7") x 36mm (1.4") x 5.5mm (0.19").

..the only real difference between CF Type I and Type II is the thickness.

Although mostly used for non-volitile data storage, the CF I/O Spec (being similar to the PCMCIA I/O Spec (Version 2.1)) allows the CF form factor (via CF+ in some cases) to be employed for other technologies such as modem, ethernet, ATA Hard drives and data collection devices. Additonally, the CF standard calls for cards that can operate in both 3.3v and 5v systems.