There are several areas that share the name 4th Floor (or a similar one):
- 4th Floor: A beta version of 4th Floor (Final). Warps from Beta Lobby C.
- 4th Floor (beta): An area connected to 3rd Floor (Beta) with many test areas in it.
- 4th Floor (Final): The titular hub with different rooms around it, with different utilities inside. Going near Toad Statue says, "Find the Core."
- 4th Floor (Corrupted): The corrupted state of 4th Floor (Final). It's dark outside, and the pipe leads to AI Undergrounds.
- 4th Floor (Fabricated): An old version of 4th floor used in v0.2.
- Floor 4B: A large, mazelike hub based on a Wasteofblood video. Warps around it lead to the corrupted state.
- Floor 4B (Corrupted): The corrupted version of Floor 4B. Peach calls in the background.
- A version of the 4th Floor is featured in the top floor of Genesis Basement.