Subnautica 2 supports online co-op for up to four players, and PC and Xbox players can join the same world through crossplay. One player hosts the world and invites friends from the in-game Friends List, while everyone else joins that host's save. The game is an underwater survival adventure from Unknown Worlds Entertainment, where you explore, gather resources, and build bases, and co-op lets you do all of that with friends.
| Setting | What to know |
|---|---|
| Players per world | The host plus up to three friends, four players in total |
| Crossplay | PC and Xbox players can play together |
| Adding cross-platform friends | Add them in the in-game Friends List with friend codes |
| Whose save it is | The host's. Guests join that save |
| Turning a solo world into co-op | Convert your save to multiplayer |
| Moving a world to another player | Use a cloud save key, which works one time |
How to Add Friends for Subnautica 2 Crossplay
Friends need to be on your in-game list before you can invite them, and this matters most when you're playing across platforms. Crossplay between PC and Xbox runs through the game's own friends system, and the same goes for PC players on Steam, Epic, or the Windows Store. Once someone is on your list, they stay there and show up every time you play, so you only need to do this once for each friend.
- Press Escape or Start, then open the Friends List.
- Select Generate Code. You only need to do this the first time you use the system.
- Select Copy Code and send it to your friend.
- Your friend pastes the code into the Friend Code box and selects Add Friend.
Either of you can start. If your friend sends their code first, paste it into the Friend Code box and select Add Friend.
How to Host a Subnautica 2 Co-op Game
Hosting turns your save into the shared world, and everyone who joins plays inside it. You can host a save you've already been playing, or start a new multiplayer save to keep your co-op adventures apart from your solo world. Pick the save before you start, since that's the world your friends will be in.
- From the main menu, select Host Multiplayer.
- Select Host New Multiplayer Game, or pick an existing save.
- Choose Survival or Creative.
- Select Host Game.
- Once you're in the world, press Escape or Start, open the Friends List, hover over your friend's name, and select Invite. Your friend can then accept it in the game.
How to Join a Friend's Subnautica 2 World
Joining is the mirror of hosting, and there are two ways in. If your friend has sent an invite, accept it in the game. If not, go to the start screen, choose Join Friends, and pick the host from your Friends List.
The host has to load the world before the co-op session can start, so you'll be waiting on them to get into their game. Friends can also drop in and out, which means you can join a world that has already been running for a while. You'll land in the world with its base and progress already built up.
Turning a Solo Save Into a Co-op World
If you've already built a base and explored alone, you don't have to start over. You can convert a single-player save into a multiplayer world, and it keeps its progress. The same switch works in reverse, so you can move between solo and co-op whenever you want.
To convert a save to multiplayer:
- From the main menu, select Play Single Player.
- Highlight your save and select Convert to Multiplayer.
- Open Host Multiplayer, select the save, and host it.
To switch a save back to solo:
- From the main menu, open Host Multiplayer.
- Select the save and choose Convert to Single Player.
Converting makes the most sense when you want to keep building on what you already have. If you'd rather keep co-op progress separate from your solo world, start a new multiplayer save instead.
What Co-op Players Share in Subnautica 2
In a co-op world, progress and structures belong to the host's save. A friend who joins is playing inside that save rather than a copy of their own. Nothing in co-op is locked to multiplayer, so everything you can do alone you can do with friends.
When the game launched, a few things were shared across the whole party:
- Storage lockers built in the world, which every player could open
- Data Entries and crafting recipes
- Vehicles
- Bases, which the group could build together or separately, with stored items not kept private
Items in your own inventory stayed personal at launch. The Buddy System update later added a way to hand those items to another player.
Voice Chat, Revives and Item Trading in Co-op
Voice chat is built into co-op, and you can set it to always on, push to talk, or always off. Pick the setting that suits how you play, whether you like to talk through a tricky dive or prefer a quieter session.
A downed friend doesn't have to lose everything. Players can revive each other before reprinting, the game's term for respawning at your assigned Biobed. A revived player keeps their equipment and gets a small amount of oxygen, while a downed player can choose to reprint right away instead.
Players can also exchange inventory items directly with each other. That makes it easy to hand gear or supplies to a friend who needs them.
How to Share Your World With a Cloud Save Key
Co-op progress stays in the save it was made in. If you step away, a friend who wants to keep the world going can't pick up your save unless you share it. Uploading your save to the cloud creates a key, and that key gives your friend their own copy to play or host.
On your side:
- From the main menu, select your save and choose Upload to Cloud.
- Select Upload and wait for the files to finish.
- When the upload finishes, you'll get a code. Select Copy Key, then press Escape to return to the main menu.
On your friend's side:
- Restart the game and select Import Save at the bottom of the main menu.
- Paste the key into the box.
- Host the copy the same way you'd host any other world.
This is a copy, not a shared save that stays in sync. Your friend's changes stay in their copy, and yours won't update to match. To pass their progress back, your friend uploads the updated copy and sends you a new key, since each key only works once.
