FF is an extension characteristic of files used by some parts of the Call of Duty game (including Black OPS II and III, Modern Warfare 3 and 4). FFs store internal game data that can be quickly loaded when you start the game. These are all kinds of data (fonts, textures, 3D graphics, etc.). FF files are not intended to be modified by the user.

Call of Duty is a series of FPS games developed by Infinity Ward and published by Activision.