How to Host & Join a Co-op Session
Short answer
Subnautica 2 co-op is host-and-play, up to 4 players. The host starts (or loads) a save, generates a Friend Code from the main menu, and shares it with friends — they paste the code under Join Friends. There is no dedicated server option in Early Access; the world only runs while the host is online.
Player cap
Up to 4 players total (1 host + 3 guests). No mods at EA expand this. The cap is a server-authority limitation, not a soft suggestion.
Host a session
- 1
Open the main menu and pick Host & Play
From the main menu, choose Host & Play instead of Single Player. You can start a new save or load any existing solo save — your solo save is automatically converted to a co-op-compatible save (a backup is kept).
- 2
Generate your Friend Code
Once you're in-game, open the pause menu → Friends tab → Generate Code. The code is a short alphanumeric string. It is per-session — restarting the game gives you a new one.
- 3
Share the code (any channel)
Discord, Steam chat, Xbox party, SMS — anything. The code is the only thing your friends need; they do not need to be on your Steam/Xbox friends list.
- 4
Accept the join request
When a friend uses the code, you'll see a prompt to approve. Approve and they spawn at your Lifepod. If approval doesn't appear, see the 'can't join' section below.
Join with a Friend Code
- 1
Main menu → Join Friends
Don't use the Steam 'Join Game' overlay — it currently breaks more often than the in-game flow. Pick Join Friends from the main menu.
- 2
Paste the code
Copy the code your host sent you (it is case-insensitive). Paste it into the join field and press Enter.
- 3
Wait for host approval
Loading screen will hang on 'Awaiting host approval' until the host accepts. If it stays there longer than ~60s, the host's session likely never received the request — see fixes below.
Crossplay PC ↔ Xbox
Friend Codes are universal across Steam, Epic, the Xbox app on PC, and Xbox Series X|S. A PC host can be joined by an Xbox guest and vice versa with no extra setup. PS5 is not supported yet — there's no PS5 build in Early Access.
Converting a solo save to co-op
Hosting from an existing solo save just works — the game writes a .coop flag into the save and keeps your inventory, base, blueprints, and progression. Going back to solo from a co-op save also works (open the save in Single Player); guests' bases stay, their inventories are unchanged because inventories are per-player.
Common 'can't join' fixes
- 1
Patch parity
Host and all guests must be on the same game version. After a hotfix, restart everyone's client before retrying — Steam/Xbox may have auto-patched one side.
- 2
Restart in this order: client → game → router
Restart the joining player's game first. If that fails, have everyone close the game completely and reopen. Router restart is last resort but fixes UPnP issues on home networks.
- 3
Switch hosts
Whoever has the most stable upload (wired, not mobile hotspot, not on Wi-Fi 2.4 GHz) should host. Host-side bandwidth is the single biggest factor in stability.
- 4
Disable overlays + antivirus exclusion
Discord overlay, MSI Afterburner, RTSS, and Razer Cortex have all been observed to break connection handshakes. Add the game folder to your antivirus and Windows Defender exclusions.
- 5
Avoid VPN
A VPN on either side causes desync within ~5 minutes. If you need a VPN for region reasons, both sides must use the same exit node.
What co-op does NOT support (EA)
- No split-screen. Online only. The most-upvoted Nolt feedback request, no ETA.
- No dedicated servers. The world only runs while the host is online; guests cannot enter when the host is offline.
- No PS5 in Early Access.
- No more than 4 players. No mod has reliably bypassed the cap.
FAQ
How many players is Subnautica 2 co-op?
Up to 4 players total — 1 host plus 3 guests. The cap is hardcoded for the EA build.
Is Subnautica 2 crossplay?
Yes — Xbox Series X|S, Steam, Epic, and Xbox app on PC all play together via Friend Code. PS5 is not yet supported.
Is there split-screen co-op?
No. Online only. There is no local couch co-op on any platform.
Are there dedicated servers?
Not in Early Access. The world only persists while the host is online. Third-party hosts (Supercraft, Nitrado, LOW.MS) sell 'host-and-play' VPS — same mechanic, just on a rented PC.