Splitscreen

4 players in splitscreen in the Doom Classic Unity port

Splitscreen is a multiplayer feature that allows multiple players to play on a single system by dividing up the screen and controls. This was added to Doom in several ports made since the original release. Given its late addition to the game, different ports will have different limitations and features to compliment it, such as different player limits and if it can be played alongside network players or not.

Officially, the feature was first introduced in the port provided alongside Doom 3 on the original Xbox, however the feature existed beforehand in community ports, namely Doom Legacy.

Official ports with splitscreen support

• Xbox
• Xbox 360
• Doom Classic (PlayStation 3)
• Doom Classic Unity port (Xbox One, PlayStation 4, Nintendo Switch, Steam, GOG, Windows Store)

All versions of splitscreen for the official port support up to 4 players in all games in both Deathmatch and co-op, but cannot be linked with network players.

Community source ports with splitscreen support

• EDGE
• Doom3D
• Doom Legacy (2 players only)
• Eternity Engine (in a development fork)
• ReMooD
• SsZDooM Split Screen ZDooM

Technical information

The method of implementing splitscreen varies between different ports. The official ports provide it by implementing the game globals as a class and creating multiple instances of the global class for each screen, each instance then connecting to each other using Doom's existing networking implementation. Community ports will typically implement it by extending Doom's understanding of the console player to support multiple players as the same "node".

A third less common method can be done by allowing a machine to run multiple instances of the same port at once, using controllers to handle the instances while out of focus. This only works on very specific platforms and has limitations in presenting sound as the instances aren't aware of each other.