DEM, Video Game Demo File (.dem)
The DEM Misc file format
The DEM file extension is most commonly associated with demo files for different video games. They are mostly used to store game replay information for first-person shooters. The most popular among them is Counter-Strike. Saved in the DEM file are video recordings from the actual game from the player's perspective. These recordings can be made in singleplayer as well as multiplayer mode. Thus, the DEM file was popular for sharing game play footage.
Technical details of DEM files
Counter-Strike is not the only game that uses DEM files. They are also utilized by Quake, Unreal Tournament, Hexen 2, Raven Shield or Half-Life. However, replay is only possible with the game the demo was made for, e.g. a Hexen 2 demo can not be viewed in Quake. To replay a DEM file, the according game has to be started after the file has been played in the games installation directory. Afterwards, it can be called using the console window. For example, in Counter-Strike, a user has to type "viewdemo filename".