Id Tech

id Tech is a series of separate game engines designed and developed by id Software. Prior to the presentation of the id Tech 5-based game Rage, the engines lacked official designation and as such were simply referred to as the Doom and Quake engines, from the name of the main game series the engines have been developed for. "id Tech" numbers 2, 3, and 4 have been released as free software under the GNU General Public License, along with the source code to Wolfenstein 3D, Doom, and Quake.

According to Eurogamer.net, "id Software has been synonymous with PC game engines since the concept of a detached game engine was first popularised." However id Tech 4 had far fewer licensees than the Unreal Engine from Epic Games, and id planned to regain the momentum with id Tech 5, until they were bought by ZeniMax Media which intends to keep the id Tech engines exclusively for id's sister studios.

id Software had developed 3D engines for several games before Doom. Each game's engine had progressively more advanced 3D technology.

Originally known as the "Doom engine", this engine powers the id Software games Doom (1993) and Doom II: Hell on Earth (1994). It was created by John Carmack, with auxiliary functions written by Mike Abrash, John Romero, Dave Taylor, and Paul Radek. Initially developed on NeXT computers, it was ported to MS-DOS for Doom's release and was later ported to several game consoles and operating systems.

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