Assetto Corsa modding revolves around a small set of standardized file formats, each serving a distinct purpose. The proprietary .kn5 format is the custom container Assetto Corsa uses to package 3D meshes, materials, and texture references into a single file the engine can load efficiently. Textures themselves use .dds (DirectDraw Surface), which allows GPU-friendly compression and mipmapping; .ini files handle nearly all text-based configuration across the game; and the encrypted data.acd archive bundles a car's physics and configuration data into a single tamper-resistant file. Modders generally unpack data.acd files using the ACD tool or Content Manager's unpack feature so that the contents can be edited.
The directory structure follows a predictable convention. Car mods live under content/cars/[car_folder_name], while track mods live under content/tracks/[track_folder_name]. Inside a car folder you will typically find a skins subfolder containing one subdirectory per livery, a ui folder for metadata and preview images, and the unpacked data folder containing all the configuration and model files. Tracks share a similar layout but add an ai subfolder containing fast_lane.ai and pit_lane.ai spline files, plus a map.png and map.ini pair for the in-game mini-map. Naming helper objects inside 3D models with prefixes such as AC_PIT_, AC_START_, and AC_TIME_ allows the engine to recognize pit spawns, grid positions, and timing lines automatically.
The core modding toolchain consists of ksEditor for converting FBX models into .kn5 files and assigning shaders, Blender or 3ds Max as the upstream 3D modeling package, and FMOD Studio for sound bank creation. ksEditor is the official utility that ingests an FBX, lets the modder assign materials and shaders such as ksPerPixelMultiMap for paint, and exports the result as a kn5 ready for the game. FMOD Studio version 1.08.12 is the traditional target for compatibility, with a guid.txt file in the sfx folder used to map FMOD event GUIDs to the text names Assetto Corsa expects. Content Manager, a community-built alternative launcher, wraps all of this together by offering mod management, validation, server hosting, and advanced settings that the vanilla launcher does not expose.