Four players means you and three friends
The ATMOSFAR coop player limit is four players total, not four guests plus the person starting the session. That allows you and up to three friends to explore together. If your regular group has five or more people, the published cap is an important detail to check before planning one shared adventure.
The official ATMOSFAR Steam description advertises both single-player and online co-op. The developer's website separately confirms a maximum of four people, matching the Steam description.
What the group can do together
The published co-op features include camping together, riding aboard a friend's Wasp, flying in formation, and working on a shared Cloud Cruiser. Those are examples of how a four-person group can cooperate, not four separate player allowances.
For example, a group does not gain extra session slots by splitting across several aircraft. Likewise, the advertised ability to share a Cloud Cruiser does not establish an unlimited number of crew members beyond the game's stated player cap.
It can help to decide who will focus on flying, gathering, or base work before a trip. That is a practical division of tasks, not a requirement that the game assign fixed classes or roles to each participant.
You can also play alone
The co-op focus does not make a full squad mandatory. Single-player is listed on Steam, and a developer response in the game's discussions explicitly confirms solo play alongside co-op for up to four people.
That means the player-count answer is a range of one to four, depending on whether you choose solo or play with friends. It does not mean every challenge or ship-management task has the same workload in either setup.
The presence of a solo mode also should not be used to infer a particular offline mode, save-transfer rule, or method of joining a friend's game. Those are separate features and procedures, not consequences of the player limit itself.
Six- and eight-player sessions are not confirmed
In a developer discussion response dated August 13, 2025, Apog Labs stated that Early Access was set to launch with a four-player cap. Asked about larger groups and possible mod support, the developer said it was too early to give a definite answer about mods.
The current official descriptions still advertise four players. A community request for six or eight players is therefore a request, not confirmation that an expanded server option exists. Do not base a purchase or group plan on a supposed modded-cap workaround without separate, current evidence.
This page answers the supported group size. It does not invent host, invite, or join-menu instructions that the cited materials do not provide.
FAQ
Is ATMOSFAR four players including the host?
Yes. Four players is the total group size: you and up to three friends, not a five-person session.
Can I play with only one friend?
The game advertises solo play and co-op for up to four people, so the published limit is a maximum rather than a required squad size.
Can five, six, or eight people play together?
The official materials used here confirm a four-player cap. They do not confirm larger sessions or a supported mod that expands the limit.
Do I need co-op to play ATMOSFAR?
No. Single-player is explicitly supported alongside online co-op.