The .demo file extension is primarily used to store recorded gameplay sessions, engine-specific test demonstrations, or executable trial versions of software applications, most notably within video games and interactive 3D graphics engines. In the context of multiplayer games like Counter-Strike, Team Fortress, or Quake, a demo file records every player movement, chat message, weapon fire, and game event as a sequence of raw network packets rather than as a traditional video. This allows users to replay matches from any camera angle, analyze gameplay strategies, or render cinematic videos at very high resolutions. Because they store game data rather than rendered pixels, demo files are typically very small in file size compared to video recordings. In other contexts, software developers or game engines may use .demo files as standalone executable files or bundled resource packages that showcase the features of a larger software product, giving users a limited-time or feature-restricted preview before purchasing the full version.