Steam

Every official Doom game and various other commercial games based on the Doom and Doom 3 engines have been released on Valve's content delivery system Steam. Most of the games were made available on August 03, 2007.

On Steam, classic Doom games and other games that use the Doom engine by default run under the DOSBox emulator, but it is also possible to use source ports with the games. More information on this below.

Some titles have had their price reduced since their introduction. Such price drops only affect the USA. For example, The Ultimate Doom and Doom II went from $9.99 to $4.99, but remained at €9.99 and £5.99. Doom 3: BFG Edition went from $29.99 to $19.99, but remained at €29.99 and £19.99. Despite the US-only price cuts, the cheapest region from which to buy Doom games on Steam remains Russia.

For a while, the Master Levels were bundled with Doom II. At one point, they were removed and couldn't be bought separately anymore. Eventually, they became available for sale independently.

Classic Doom games

 * The Ultimate Doom ($4.99 / 9,99€ / £5.99)
 * Doom II ($4.99 / 9,99€ / £5.99)
 * Master Levels for Doom II ($14.99 / 14,99€ / £9.99)
 * Final Doom ($4.99 / 4,99€ / £3.99)

Doom engine games

 * Heretic: Shadow of the Serpent Riders ($4.99 / 4,99€ / £2.99)
 * Hexen ($4.99 / 4,99€ / £2.99)
 * Hexen: Deathkings of the Dark Citadel ($4.99 / 4,99€ / £2.99)
 * Note: Contrarily to all other Doom-engine games available on Steam, this version of Deathkings is not the latest and requires the to work correctly.

Doom 3
Note: Ownership of the normal Doom 3 on Steam gives a 33% discount when buying the BFG edition.
 * Doom 3 ($9.99 / 9,99€ / £5.99)
 * Doom 3: Resurrection of Evil ($4.99 / 4,99€ / £3.99)
 * Doom 3: BFG Edition ($19.99 / 29,99€ / £19.99)

Doom 3 engine games

 * Quake 4 ($19.99 / 19,99€ / £14.99)
 * Brink ($19.99 / 19,99€ / £14.99)

Collections

 * Doom Classic Complete ($14.99 / 14.99€)
 * Doom 3 Pack ($12.99 / 12.99€ / £7.99)
 * Heretic + Hexen Collection ($9.99 / 9.99€ / £5.99)

Doom 3 engine games

 * Prey (was not available in the UK, but could be activated via retail CD key)
 * Enemy Territory: Quake Wars
 * Wolfenstein

Collections

 * Doom Pack Complete - included all PC Doom games, up to Resurrection of Evil
 * Id Super Pack - included all id Software games and several from Raven Software, up to Return to Castle Wolfenstein
 * Super id Software Pack - superseded the Id Super Pack, including the same games and adding Rage and Quake 4.

How to use source ports with games downloaded from Steam
Some source ports automatically check the system registry for Steam's install folder, and will search it for the game IWADs. These include:
 * Chocolate Doom
 * Eternity Engine
 * GZDoom
 * Odamex
 * Skulltag
 * Zandronum
 * ZDoom

For other source ports, the following steps are necessary:

First, download the archive that contains the source port executable and other files necessary to run it. Then decompress the source port archive, and put all the files/folders into the folder \SteamApps\Common\\base. Running the source port main executable (for example, zdoom.exe or prboom.exe) should then start the game.

Alternatively, the IWAD (named doom2.wad for Doom II, hexen.wad for Hexen, etc.) can be copied from \SteamApps\Common\\base to a directory of your choosing and the source port files decompressed/copied there. Again, running the source port main executable should then start the game.

If you wish to run the games with a source port via Steam or its shortcuts, you need to decompress and copy the source port files to <Steam directory>\SteamApps\Common\<game name>\base</tt> as instructed above. Then you need to rename or delete dosbox.exe</tt> and rename the port's executable to dosbox.exe</tt>. After this the Steam shortcut will launch the game via the chosen source port. Steam's overlay will work with hardware accelerated ports, and Steam Cloud support for synchronizing saves between PCs will continue to work as long as the port uses the .dsg</tt> extension for its saves.