The player limit in Totally Safe Moon Project is five people in a session: you and four friends. The cap is fixed and the host cannot raise it, because it exists to keep the world in sync. To invite friends, walk to the "Invite Friends" board on the garage wall and press E, or press I from anywhere in the world to open the same invite screen.

Totally Safe Moon Project player limit: five in a session

  • Five players in total — you plus four friends.
  • The host cannot lift the cap. It is a hard limit rather than a lobby setting.
  • The reason given for it is to avoid synchronization issues, which is why it does not scale with how many friends you have.

Online Co-op is listed alongside Multi-player and Co-op as a feature, and a co-op session is the same world you build the tower in — everyone works on the same stack, in the same street, so the tower building guide applies to the whole group.

Totally Safe Moon Project how to invite friends

There are two ways in, and the second one saves you a walk.

  1. The garage board. A sign on the garage wall reads "Invite Friends", and the prompt on it is "Interact" on the E key. Walk up and press E.
  2. The shortcut. A banner across the top of the screen reads "PRESS I TO INVITE FRIENDS", so pressing I opens the invite screen from wherever you are standing — no need to climb back down to the garage.

What a partner changes on the climb

The extra players are carrying capacity, mostly. Every prop in the tower has to be hauled up by somebody, and with four extra people you can keep building while others carry, and carry while others place.

The second thing a partner gives you is the Magnet's "Pull Player to you", which drags a teammate toward you when they are stranded below the stack — the tools to equip guide has the full hotbar setup.

Four co-op players hauling a green garbage truck, a bus and a pickup truck above the suburban town, with a rocky mountain behind them.
Extra players are carrying capacity: some haul props up while others place them.

Playing it alone

Nothing in the core loop needs a second player: the height ladder, the "NEXT GOAL" banner, the garage upgrade terminal, the tool grid and the laser delivery all work the same way on your own. The single player guide covers what a solo run looks like and what you give up by not sharing the work.