See also: Teleportato
Maxwell's Door is a portal that transfers a player from Sandbox Mode to Adventure Mode. It is surrounded by Evergreens, Fireflies, and Evil Flowers. When the player goes near it, the machine will become active, appearing as Maxwell's face. It resembles the machine which brought Wilson to Maxwell's world in the first place, as seen in Forbidden Knowledge video. It can be found with the help of a Divining Rod.Upon activating it, a warning message will appear informing the player about Adventure Mode and asking them if they want to proceed or not. If they do, the player will be grabbed by a Shadow Hand and then appear in the first chapter of Adventure Mode with no inventory (except special items such as Lucy, Willow's Lighter, or Abigail's Flower) or recipes, so players are required to begin anew in Adventure Mode. Health, Hunger, and Sanity levels will be restored, however. If the player dies in Adventure Mode, they will wake up in front of the Maxwell's Door in Sandbox Mode with their original inventory, Health, Hunger, and Sanity level as if they never activated the Door.
- Maxwell's Door was added to the game with the Doorway to Adventure update.
- Getting close to the Door the faint tune of the Ragtime song can be heard (referring to the epilogue of Adventure Mode, with the Gramaphone).
- When Wilson examines Maxwell's Door, he says, "I'm not sure I want to fall for that a second time." This is a clear reference to his origin video.