AIN file format is used by games that run on Source engine. Source is a 3D game engine availbale for many differnt platforms, including game consoles. More that 30 FPS games were created using Source engine (Half-Life trilogy, Conter Strike, Titanfall, and many others).

AIN file stores data used by game’s artificial intelligence and defines behaviour of NPCs and player enemies during gamplay. AIN file defines how such objects should move on the map. AIN files are automatically generated by the game.