Subnautica has no official multiplayer — so co-op runs on Nitrox, a community-made mod that adds a server plus a client every player installs. Falix hosts the server side for you; this guide gets it running, points you at the admin password the panel generates, and walks the part people miss: everyone needs the matching Nitrox client, or they can't join.
| At a glance | |
|---|---|
| You need | A free Falix account, and Subnautica installed on each player's PC |
| Time | About fifteen minutes |
| Plan | Free — the Nitrox server runs on the free plan |
⚠️ Heads up: Nitrox is a community project still in active development. Expect the occasional bug, desync, or rough edge — that's the nature of unofficial multiplayer, not something you broke. Back up your save regularly and keep the whole group on the same Nitrox version.
Step 1: create the server
Go to Servers → Create server, open the Games tab, and choose Subnautica. The panel installs the Nitrox server for you. (New to the create page? The Knowledge Base has a walkthrough.)
Step 2: check your variables (and grab the admin password)
Open the Settings page, Environment tab — a server's variables live here, editable on every plan. The ones that matter:
| Variable | What it does |
|---|---|
SERVER_MODE |
Game mode — default SURVIVAL (Subnautica's other modes exist too, e.g. Freedom, Hardcore, Creative) |
SUBNAUTICA_PASSWORD |
Join password — blank by default (no password); set one to lock the server |
SUBNAUTICA_ADMIN_PASSWORD |
Auto-generated admin password — read it here when you need admin commands |
SAVE_NAME |
The save file name (default world) |
NITROX_VERSION |
Which Nitrox build the server runs (latest is fine) |
SAVE_INTERVAL |
How often the world auto-saves, in milliseconds |
🎯 Good to know: The admin password is generated for you at install and shown right here in the variables — you don't set it, you just copy it. It's what authenticates admin commands in-game, so grab it when you need to run one.
Step 3: start the server
Press Start and watch the Console page. The Nitrox server loads and begins hosting. On the first boot it creates the save from SAVE_NAME; later starts load that same save. Once the console shows it up and listening, the server side is ready.
Step 4: every player installs the Nitrox client
This is the step that makes or breaks a join: the server alone isn't enough — each player installs the Nitrox mod into their own copy of Subnautica.
- Everyone downloads Nitrox from the official site, nitrox.rux.gg (the download page has the installer; Nitrox is open source, with its code at github.com/SubnauticaNitrox/Nitrox).
- Run the Nitrox installer/launcher, which patches Subnautica for multiplayer.
- Match versions: every player must be on the same Nitrox version as the server (
NITROX_VERSION). A mismatch is the number-one reason a join fails.
Step 5: join
Launch Subnautica through Nitrox, choose to join a server, and enter your address and port from the Network page (Subnautica/Nitrox has no name-only shortcut, so include the port). If you set SUBNAUTICA_PASSWORD, players enter that too.
⚠️ Heads up: Include the port from the Network page, not just the address.
What survives, and what doesn't
Your Nitrox save lives in the server's files and survives restarts, stops, and the free-plan sleep. A reinstall — or switching the server to a different game — wipes it. Because Nitrox is still maturing, a backup is extra worthwhile here: take a backup before updates or big sessions; on free, backups save to your own Google Drive.
Verify it works
The Console shows the server hosting; when a player on the matching Nitrox client connects with address:port, their join appears in the log and you'll see each other in-game. If someone bounces off, it's almost always a Nitrox version mismatch or a missing port — check those first.
Troubleshooting
- A player can't join — their Nitrox version doesn't match the server's
NITROX_VERSION, or they didn't include the port. Get everyone on the same Nitrox build and useaddress:port. - Where's the admin password? — it's the auto-generated
SUBNAUTICA_ADMIN_PASSWORDon the Environment tab; copy it from there. - Desyncs or odd bugs — expected with in-development software. Keep everyone on the same version, and report reproducible issues to the Nitrox project.
- Server stopped on its own — free-plan behavior: it stops when empty and gets roughly a 60-minute grace window when unreachable. Revive it from the Timer page — How free game servers work.
For client install help, current version notes, and troubleshooting, the source of truth is the official Nitrox site, nitrox.rux.gg.