Files with the .ADI extension contain a backup copy of a hard drive or of another memory storage unit, saved in a compressed format in a way that requires only selecting, not moving, free sectors. The files can contain a full copy or only a fragment of one, and can also only contain a selected part of system data. ADI backup copies are created by the Active@Disk Image software, which is also used for data and system recovery.

They are characterized by good data compression, and their archives can be divided.