Doom modding

Doom modding is the creation of modifications for the first-person shooter games *Doom* and *Doom II: Hell on Earth* by id Software. Players can build new levels, alter graphics and sounds, and tweak gameplay mechanics. This practice is a core part of the series' identity and helped make modding more common and accessible across gaming, not just in first-person shooters. During *Doom*'s development, id Software designed it to be easy to modify. Game content was kept separate from the engine in WAD files—a format whose name stands for “Where’s All the Data?”. This allowed new content to be created and shared without patching the game or writing code. There are two types of WADs: IWADs, which hold the data needed to load the game, and PWADs, which contain add-on content like new sprites, weapons, and other material. After *Doom*’s 1993 release, a large community of players began making and sharing WADs. In 1997, id Software released the *Doom* engine source code (re-licensed under the GNU GPL in 1999). The community then developed source ports—modified versions of the engine that expanded the original game’s technical limits. These enabled new modding possibilities, such as advanced scripting, 3D environments, and modern rendering features. As a result, *Doom* modding has stayed very active long after the game’s release. While mods exist for later series entries like *Doom 3* and *Doom Eternal*, modding has mainly focused on the first two games. Thousands of mods have been created, from small levels to full original games. Most are freely shared and downloadable online, and several have been released commercially. Some modders later became professional game developers, joining commercial studios. When creating *Doom*, id Software knew many players had tried to make custom levels for their earlier game *Wolfenstein 3D*, but the process was cumbersome. Lead programmer John Carmack designed *Doom*’s internals from the start to let players extend the game. Game assets, levels, and other content were separated from the engine in WAD files. Tom Hall came up with the name “WAD.” The idea of easy modding was mainly backed by Carmack, a supporter of copyleft and the hacker ideal of sharing and building on others’ work, and by John Romero, who had hacked games as a youth and wanted to allow others to do the same.