id Tech 3 originally debuted with Quake III: Arena and was further extended and enhanced during the developments of Quake III: Team Arena and Heavy Metal F.A.K.K. 2. id Tech 3 introduced some state-of-the-art features back when it was developed. Some of them were the support of a shader system, loading character models in three parts for more flexible animations, and last but not least, a hardware accelarated renderer. This required the users to upgrade their PCs, a trend that would repeat itself over the next decade, time and time again. id Tech 3 used the gtkRadiant editor.
Today, the most prominent users of the id Tech 3 engine are Activision based developers, Infinity Ward and Treyarch. Within Infinity Ward's Call of Duty series, the modified engine is known as the IW Engine. The most innovative upgrades include a streaming system, an upgraded shader library, and a real time physics engine.