Freedoom is a Free IWAD file that can be used to play Doom without the original proprietary game files. However, it requires a Boom-compatible engine to run. Because Chocolate Doom is only compatible with Vanilla Doom, Freedoom does not run properly with Chocolate Doom.
However, Chocolate Doom can still be made to run with Freedoom. The only incompatibility between the two is that the levels distributed with Freedoom do not run. Because of this, Freedoom will run without problems provided that replacement levels are always loaded.
An alternative is to use the FreeDM IWAD, which is a version of Freedoom that contains only multiplayer deathmatch levels; these levels are Vanilla-compatible.
- Download and extract Chocolate Doom.
- Download and extract Freedoom, and copy the freedoom2.wad file into the Chocolate Doom folder.
- Find a megawad or TC, that replaces all 32 levels of Doom 2 (Map01 - Map32), and load it in the normal way with the -file parameter. For example:
chocolate-doom -iwad freedoom2.wad -file filename.wad
 Suggested MegaWADs
The idgames archive is a good place to find WADs to play with. Not all levels will work with Chocolate Doom - look for levels that are marked as "Vanilla compatible", will run with "Doom 1.9", or "no advanced engine required".
 Doom 2 MegaWADs (for doom2.wad)
|Icarus: Alien Vanguard||icarus.zip|
|Memento Mori II||mm2.zip|
More Doom 2 MegaWADs can be found in the levels/doom2/megawads/ directory of the /idgames archive.
 Doom 1 MegaWADs (for doom.wad)
|2002: A Doom Odyssey||2002ado.zip|
|Doom the Way id Did||dtwid.zip (Doesn't currently work in the latest stable release because of a Freedoom bug. However, it has been fixed in the trunk.)|
More Doom 1 MegaWADs can be found in the levels/doom/megawads/ directory of the /idgames archive.