The Doom Editing Utilities were among the first level editors for Doom in 1994, and being open source were used as the basis of numerous forks, including the modern cross-platform Eureka. DEU was used in the development of the 3DO version of Killing Time, with the level data then converted to its specialized ZX engine.
It has since been competed with by other editors such as the Doom Builder family and SLADE. The actual DoomEd used internally by id Software was finally publicly released in 2015, leading to a fork called ReDoomEd in 2020.