A save game in the Doom engine takes a snapshot of the current game state and saves it to one or more files, allowing the player to resume precisely at the point the save was performed. These files are not usually portable across multiple versions, source ports, or CPU architectures (such as between PowerPC and x86), with few exceptions.
In the vanilla Doom games, save games are a single file per save, named doomsavN.dsg, where N is a numeral of 0-5 depending on the position of the in-game save menu.
Doom has a few engine bugs that prevent save games from working completely as expected. A common manifestation occurs in MAP24: The Chasm (Doom II), where unsuspecting players saving on the narrow ledges would find their save games useless after reloading.
- Moving platform heights not preserved in saved games
- Retriggering an open door after loading a savegame causes crash
- Savegame buffer overflow
- Sector type 17 is disabled after loading a saved game
- Some game options not preserved in saved games
- Spawn spots not preserved in saved games
- Targets not preserved in saved games
In Heretic, save games are a single file per save, like Doom, and named hticsavN.hsg, where N is a numeral of 0-5 depending on the position of the in-game save menu.
Source port compatibility
Most source ports expand upon the save game format, adding new features and fixing bugs of the original, disregarding compatibility with the vanilla engines. One notable exception is Chocolate Doom, which maintains cross-compatibility with saving and loading vanilla-format save games, even on differing CPU architectures.