Multi-User Dungeons (MUDs) are persistent, text-based multiplayer virtual environments — among the earliest forms of online shared spaces and the direct ancestors of MMORPGs and virtual worlds. This topic covers MUD history and architecture, the driver separation that defined MUD software engineering, and the distinctive insight that world-building and programming are the same act.
MUDs are computing artifacts, not just games. The separation of engine from content library — the mudlib architecture pioneered by LPMud — anticipated patterns that later appeared in web frameworks, game engines, and content management systems. The text-based interface means that the world exists entirely as language and computation, making MUDs a site where semiotics and software converge.