Id Tech

id Tech is a series of successive game engines designed and developed by id Software. They are used in many of id Software's games, such as games in the Doom, Quake and Wolfenstein franchises, and has been also licensed to other developers. Several notable game engines, such as GoldSrc or the IW engine originate from id Tech code. Earlier game engines up to id Tech 4 have been released as free software under the GNU General Public License (GPL-2.0-or-later until 2005, GPL-3.0-or-later until 2012). id Tech 5 to 8 remain proprietary, with id Tech 8 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 Unreal Engine from Epic Games. id planned to regain the momentum with id Tech 5, until the company was bought by ZeniMax Media in 2009 (who was later bought by Microsoft in 2021), with both companies choosing to keep the id Tech engines exclusively for id and its sister studios as a proprietary engine.