What is a VMAT file? A VMAT file is a material file used by the Valve Source 2 game engine, which is used to create video games. It contains references to .VTEX_C files, as well as data specifying shader and material properties. Player-created VMAT files are created by the Material Editor, which is included in the Dota 2 Workshop Tools and Half-Life: Alyx Workshop Tools utility packages.

More Information Source 2 is a proprietary game engine Valve has used to create video games such as Dota 2 Reborn, Half-Life: Alyx, and Artifact. When creating in-game objects, developers use VTEX_C and VMAT files to apply materials to those objects. VTEX_C files contain the texture(s) that appear on an object, and VMAT files contain references to VTEX_C files as well as shading and material properties that control how textures appear when applied to a specific object. While most gamers will never encounter a VMAT file, those who want to mod Valve Source 2 games or create their own Source 2-powered games may interact with VMAT files. For example, those who want to mod Half-Life: Alyx or Dota 2 using Valve's official modding toolkits may encounter or create VMAT files.