Game data file used by Doom and Doom II, as well as other first-person shooter games that use the original Doom engine; contains data such as sprites (graphics), level information, and items; used for storing original game content as well as game modifications.

The WAD format has been classified into two categories: 1) IWAD ("Internal WAD") and 2) PWAD ("Patch WAD"). The IWAD file type is used for loading core game content, and PWAD files are used for adding optional data to the game. Because of the popularity of Doom and the customizability of WAD files, the WAD format became one of the more widely known and widely used game data file formats. Community gamers developed thousands of mods using WAD files for Doom and other games. However, since Doom and Doom II were released in the 1990s, the format is not as commonly used as it once was. The original WAD format, referred to as WAD1, evolved into subsequent formats, which include WAD2 and WAD3. These versions were reduced in scope to include only game textures and were used for Quake and Half-Life. Quake WAD texture files can be edited with programs such as Wally.