Id Tech

id Tech is a series of successive game engines designed and developed by id Software. Prior to the presentation of the id Tech 5-based game Rage in 2011, the engines lacked official designation and as such were simply referred to by the names of the games the engines had been developed for (i.e., Doom and Quake engines). The id Tech engines up through 4.5 have been released as free software under the GNU General Public License. id Tech versions 0 to 3 were released under GPL-2.0-or-later; id Tech versions 3.5 to 4.5 were released under GPL-3.0-or-later. id Tech 5 to 7 remain proprietary, with id Tech 7 currently being the latest engine.

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. id planned to regain the momentum with id Tech 5,^[1] until the company was bought by ZeniMax Media, which chose to keep the id Tech engines exclusively for id and its sister studios.