nonplayer

Nonplayer, often written as non-player character or NPC, refers to a character in a game or simulation that is controlled by software rather than by a human player. NPCs populate the game world to provide interaction, information, quests, services such as merchants or trainers, and various challenges or aid for the player. They can be allies, enemies, or neutral observers and may advance the story, supply lore, or enrich world-building.

Common NPC roles include townsfolk, merchants, guards, quest givers, companions, and bosses. Some NPCs are essential to the main storyline, while others serve as ambient flavor or random encounters. The behavior and utility of NPCs help pace gameplay, offer tutorials, and create a sense of a living world.

Artificial intelligence for NPCs has evolved from simple scripted sequences to more sophisticated systems. Early games used predetermined dialogues and fixed actions, while modern titles employ techniques such as finite-state machines, behavior trees, utility systems, and planning algorithms. Pathfinding with navigation meshes, perception models (like line of sight and hearing), and contextual dialogue decisions contribute to more believable and responsive characters.

Design considerations for NPCs include writing believable dialogue, ensuring consistent character motivation, performance optimization, and localization. Representation and inclusivity are also important to avoid stereotypes and to reflect diverse player experiences. NPCs are contrasted with player characters, which are controlled by human players, and they interact with players through combat, trade, companionship, or information exchange. Outside entertainment, nonplayer agents appear in simulations and training environments to model autonomous agents that interact with humans or other AIs. See also: NPC and player character.