Game engines have come to feature in areas well beyond gaming—such as architecture, artificial intelligence, manufacturing, public planning, and film and television production. Accordingly, companies developing, providing, and maintaining game engines—such as Epic Games or Unity Technologies—are set to become influential actors in all social and economic arenas that start to rely on game engines for the provision of software or services. This makes them an important subject to the study of platforms as they provide increasingly crucial building blocks in the digitization of economic, political, and social life. In this article, we present three dimensions demonstrating platform functions of game engines beyond gaming. We rely on the example of two important game engine developers: Epic Games and Unity Technologies. The dimensions are (1) the growing area of extended reality applications, (2) cross-platform and cross-media story- and brand worlds, and (3) the management of user payments, identities, and social graphs. The article shows how companies providing game engines challenge the current balance of power between established platform companies, demonstrating that game engines have emerged as an important new type of platform that demands academic and public attention.