Call of Duty, a popular first-person shooter video game franchise, has historically used a variety of engines. Initially, it started with the id Tech 3 engine for the early games but recent titles like Call of Duty: Modern Warfare (2019) and Call of Duty: Warzone have been developed using a heavily modified version of the IW engine, known as the IW 8.0.
These modifications are significant and make their engine quite different from the original IW engine. They include enhancements to the rendering system, audio design, physics simulation, and more. This allows them to achieve higher visual fidelity, realistic acoustic environment simulation, physically-based material system, and dynamic lighting and shadows, among other things.
Please note that the specific engine used can vary between titles and the development studios involved, and newer versions of Call of Duty may use updated or different engines.