.DEM File Extension

There are 3 file types use the .DEM file extension:

  1. Video Game Demo File
  2. Digital Elevation Model
  3. Unreal Engine Game Replay File

1. Video Game Demo File

Video Game Demo File

A DEM file is a game replay file created by various first-person shooter games and most popularly by Counter-Strike (supported by Valve's Source game engine). DEM files are used to record a player's perspective in a single or multiplayer game, which can then be shared with others.

To play a Counter-Strike DEM file in Windows, first place it in the cstrike\ installation directory. Next, start Counter-Strike and open the console window. From the console window, type viewdemo demoname, where "demoname" is the filename without the ".dem" extension.

DEM files are also used by Hexen II and Quake. A separate subset of DEM files are used by Unreal Engine games, such as Unreal Tournament. However, the files are only playable on the game for which the demo was created.

NOTE: DEM files created by Source engine games, such as Counter-Strike, can be opened in VirtualDub to play the video frame sequence and record it to other output formats, such as .AVI. There is a size limitation of 2 GB for AVI videos created by Valve's source engine. You can install the Apple QuickTime component to encode the .H264 codec in order to avoid the size limitation.

Software's name License Platforms
Epic Games Unreal Tournament Epic Games Unreal Tournament Commercial MacWindows
id Software Hexen 2 id Software Hexen 2 Paid Windows
id Software Quake id Software Quake Paid MacWindows
Valve Counter-Strike Valve Counter-Strike Paid MacWindows
VirtualDub VirtualDub Free Windows

Updated: January 9, 2016

2. Digital Elevation Model

Digital Elevation Model
  • Developer USGS
  • Popularity
    3.9 (72 votes)
  • Category GIS Files
  • Format N/A

Contains mapping data with elevation information; used by the US Geological Survey.

Software's name License Platforms
ESRI ArcGIS for Desktop ESRI ArcGIS for Desktop Commercial Windows
Golden Software Voxler Golden Software Voxler Commercial Windows
MicroMouse AccuTrans 3D MicroMouse AccuTrans 3D Free Trial Windows
TatukGIS Viewer TatukGIS Viewer Freeware Windows

Updated: August 5, 2012

3. Unreal Engine Game Replay File

Unreal Engine Game Replay File
  • Developer Epic Games
  • Popularity
    3.0 (1 votes)
  • Category Game Files
  • Format Binary

A DEM file is a video game replay created by a game that uses the Unreal Engine, a game engine developed by Epic Games. It contains data used to playback a recording of a player's gameplay. DEM files are created and played using the Unreal Engine's Console, which can be accessed by pressing the ~ key while playing a game.

The Unreal Engine gives game developers and players access to Console commands that allow them to record, playback, and examine their gameplay. For example, developers who want to check their games for bugs may want to record their gameplay to note when, where, and how bugs arise, and players may want to record their gameplay to note play mistakes and help themselves improve. To begin recording a replay within an Unreal Engine game, players can press the ~ key to open the Unreal Engine Console and enter the command demorec yourdemofilename. This will create a DEM file.

To stop recording a replay, players can enter the command demostop. Players can then play their DEM file by entering the command demoplay yourdemofilename. (Do not include the .dem extension as part of the filename.) If you forget your DEM file's filename, you may be able to find it by looking in your game's Saved directory, which is often used to store DEM files.

NOTE: All games created with Unreal Engine 4 include the Replay System used to create DEM files. Games created with earlier versions of Unreal Engine may or may not include the Replay System, depending on the game. Unreal Tournament does include the Unreal Engine Console and Replay System.

You can play a DEM file in the Unreal Engine game that created the file. For example, if you created a DEM file while playing Unreal Tournament, you can play that DEM file by opening the Unreal Engine Console in Unreal Tournament (by pressing ~ while at the game's main menu) and entering the command demoplay yourdemofilename. (Again, do not include the .dem extension as part of the filename.) Some third-party programs, such as UT Demo Manager, can help players more easily open and play DEM files in specific games.

Software's name License Platforms
Epic Games Unreal Tournament Epic Games Unreal Tournament Commercial MacWindows
Other Unreal Engine games Other Unreal Engine games MacWindows
UT Demo Manager UT Demo Manager Free MacWindows

Updated: March 18, 2021

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