Doom modding

Doom modding is the practice of creating modifications for games in the first-person shooter franchise Doom developed by id Software, such as the original Doom and its sequel, Doom II: Hell on Earth. These modifications allow players to design new levels, change graphics and sounds, and adjust gameplay mechanics.

During the development of Doom, id Software designed the game to be easier to modify and change; game content was separated from the engine itself. Levels, textures, sounds, and other game data were packaged as WAD files. The name "WAD" stands for “Where’s All the Data?”. The WAD format made it possible to create and share new content without patching the game or writing code. There are two types of WADs: internal and patch WADs (IWAD and PWAD). An IWAD contains the data necessary to load the game, while additional PWADs contain add-on data, such as more character sprites, other weapons, and other content. Immediately following Doom's release in 1993, it attracted a sizeable following of players who created and shared WADs.

Following id Software's release of the Doom engine source code in 1997 (and its re-licensing under the GNU GPL in 1999), the community began developing modified versions of the engine called source ports. These expanded the technical limits of the original game and enabled new forms of modding, including advanced scripting, 3D environments, and modern rendering features. As a result, Doom modding has remained very active well past its release date. Although mods exist for later games in the series, such as Doom 3 and Doom Eternal, modding has continued to focus on the first games.

Doom modding is considered a significant portion of Doom's identity, and has played a vital part in making modding more accessible and commonplace in gaming, including games other than first-person shooters. Thousands of mods have been created, ranging from small levels to full original games; most of these are freely shared and downloadable on the internet. Several mods have also been released commercially. Some modders later became professional game developers, with several joining commercial studios.