SHADER is an extension used by computer games based on the id Tech 3 engine. SHADER are files that are responsible for the way graphic objects are shaded in the game. They are used to define the properties of texture shading. Technically, SHADER is a plain text file that can be opened in any editor.

id Tech 3 is the engine on the basis of which many famous game titles were created, such as Quake 3 Arena, Return to Castle Wolfenstein and Medal of Honor.