MBF adds several features:
- Friendly monsters, including single-player helper dogs.
- Bug fixes, such as a fix for the blockmap limit (MBF includes an internal blockmap builder).
- A "beta" mode, in which MBF emulates the behaviour of beta versions of Doom. This includes the version of the BFG9000 included in the beta.
- Higher-resolution 640x400 screen mode.
- A means to change the level's sky texture (Linedef action 271)
Due to changes in the collision detection algorithms, a respawned or resurrected monster can sometimes become "glued" to another monster or to a wall. This bug propagated into later ports which used the MBF source, such as PrBoom.
- Artica series -- PWADs that utilise the MBF "friendly" bit