You can host Subnautica multiplayer without paying a monthly server bill by running the free, open-source Nitrox modification on a computer you control. You still need a legitimate PC copy of the original Subnautica game. Install Nitrox, launch NitroxLauncher as administrator, choose Server → Start Server, then give friends the address shown by the server. Remote players normally need access to the host through UDP port 11000, either by router port forwarding or a virtual private network such as Hamachi.
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What “free Subnautica server” actually means
Nitrox is an open-source multiplayer modification for the original Subnautica; it is not an official multiplayer mode made by the game’s developer. The modification and its server software are free to download. Self-hosting also avoids a required recurring hosting charge because the server runs on your own computer and home connection.
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What you need before starting
- A PC installation of the original Subnautica game.
- The current Nitrox release installed on the host and on every player’s PC.
- A computer that can remain running while friends play.
- Permission to change the host router or, alternatively, a VPN that places the players on a shared virtual network.
- Firewall rules that allow the game and Nitrox server processes to communicate.
Nitrox’s homepage listed version 1.8.1.0 as the latest release in the 2026 page capture used for this guide. Check the project’s current release before installing, because compatibility and stability can change while the project is being developed.
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How the free self-hosted setup works
The host runs two things: the Nitrox server process and the game client. The server maintains the multiplayer world, accepts connections, saves the world, and exposes a network port. Friends run Nitrox on their own computers and connect to the address displayed by the host’s server window.
Inside the same home network, players can often connect using the host computer’s local address. Players on the internet need a route into that network. The standard Nitrox configuration uses UDP port 11000. A router port-forwarding rule sends traffic arriving on that port to the computer running NitroxServer-Subnautica.exe.
Some routers support UPnP, and Nitrox advertises automatic port forwarding through UPnP. Whether it works depends on the router, its UPnP setting, and the network topology. If automatic mapping fails, create the forwarding rule manually or use a VPN instead.
Install Nitrox and start a server
- Install the game. Install the original PC version of Subnautica through your game store and run it once so its files and first-launch settings are created.
- Install Nitrox. Download the current Nitrox release from the project’s official distribution channel and install it on the host PC and on each friend’s PC. Keep everyone on the same Nitrox release.
- Open the launcher with elevation. Right-click
NitroxLauncherand select Run as administrator. Administrator access helps the launcher and server create their network and game integrations correctly. - Open the server controls. In NitroxLauncher, select Server, then choose Start Server.
- Configure the session. Set a password if you want a private game. Nitrox also supports configurable game modes, public mode, and a server console. Leave the console running while the session is active.
- Copy the displayed address. The server window shows the address players should use. Give that address and the password, if one is set, only to the people you want to join.
- Launch the game through Nitrox. Each player starts NitroxLauncher, selects the multiplayer connection option, and enters the host address shown by the server.
Do not close the server window when you launch the game. Closing it stops the process that owns the world and disconnects everyone.
Make the server reachable from the internet
Option 1: Router port forwarding
Port forwarding is the normal direct-hosting method. The exact menu names differ by router, but the information is the same:
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- Give the host computer a stable local address. A DHCP reservation in the router is preferable to relying on an address that can change after a reboot.
- Open the router’s administration page and find Port Forwarding, Port Mapping, or a similarly named section.
- Create a rule that forwards UDP 11000 from the internet to the host computer’s local IP address and UDP port
11000. - Save the rule and restart the Nitrox server if the router requires it.
- Share the public address displayed or identified by your setup, not the host’s private address such as
192.168.x.x, with friends outside your home.
Nitrox’s hosting guidance specifically identifies UDP 11000 as the required port. Do not substitute TCP unless a later Nitrox release documents a different requirement. Some routers let you specify a port range; for a standard installation, a single UDP rule for 11000 is the relevant mapping.
Option 2: UPnP
Nitrox advertises automatic port forwarding through UPnP. If UPnP is enabled and supported by the router, the launcher may create the mapping without a manual rule. UPnP is not guaranteed: carrier-grade NAT, double-router installations, restricted ISP equipment, or disabled UPnP can prevent it from working. Know how to remove a stale UPnP mapping and use manual forwarding or a VPN when automatic setup fails.
Option 3: A virtual private network
A VPN such as Hamachi can place the host and players on a shared virtual network. This avoids changing the home router and is useful when the ISP uses carrier-grade NAT or the host does not control the router. Everyone must install the same VPN client, join the same virtual network, and use the host’s VPN address when connecting.
A VPN adds another dependency and can increase latency. It also does not remove the need for firewall rules. Allow the VPN application and the Nitrox processes through the operating system firewall, and use a private VPN network rather than sharing an open public network.
Allow Nitrox through the firewall
Windows Firewall can block a correctly forwarded port. Create or approve inbound and outbound rules for both the game and the server executable named in Nitrox’s hosting guide:
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Subnautica.exeNitroxServer-Subnautica.exe
When Windows first displays a network-access prompt, allow the programs on the network profile you actually use. If the prompt was dismissed, open Windows Security → Firewall & network protection → Allow an app through firewall and add the executables. For a more restrictive setup, create an inbound UDP rule for local port 11000 and limit it to the required network profiles.
After changing firewall or router rules, stop and restart the Nitrox server. Test from a friend’s network or a phone hotspot; testing only from inside the same Wi-Fi can succeed even when internet access is still blocked.
Choose the right access model
| Method | Monthly server fee | Internet setup | Availability | Who maintains it |
|---|---|---|---|---|
| Self-host with forwarding | No required hosting fee | UDP 11000 forwarded to your host | Only while the host PC and connection are running | You |
| Self-host with UPnP | No required hosting fee | Router must successfully create a UPnP mapping | Only while the host PC and connection are running | You and the router |
| Self-host through a VPN | The Nitrox server is free; VPN terms depend on the VPN service | All players join the same virtual network | Only while the host PC and connection are running | You and the VPN service |
| Third-party public server | Not established by Nitrox’s official sources | Provided by the operator | Depends on that operator | The server operator |
| Managed commercial host | Provider-specific and not established here | Provider-specific | Usually designed for continuous access, subject to the provider’s terms | The provider, with your account controls |
When evaluating a paid managed host, compare the monthly price, player-slot limit, region and latency, backup controls, Nitrox version support, port exposure, and technical support. Nitrox’s official sources do not verify current provider prices, locations, or service quality, so those details must be checked directly with any provider before purchase.
Capacity, settings, and save behavior
Nitrox’s server feature page documents support for up to 100 connected players, while recommending five players. The 100-player figure is a documented maximum, not a recommendation for an ordinary co-op group. Your hardware, upload capacity, world activity, and software stability can make a smaller practical limit more appropriate.
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The server includes a console and built-in chat. You can configure the port, enable automatic saves, select game modes, and choose public or password-protected private operation. Before inviting people, set a password for a private session and confirm that automatic saves are enabled. A password protects access; it does not replace backups or moderation.
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Self-hosting means the world is available only when the host machine, Nitrox server, router, and internet connection are working. Sleep settings, Windows updates, reboots, power loss, and a changing public address can all interrupt access. For a short co-op session, starting the server when friends are ready is usually simplest. For regular access, use a machine that can stay powered, schedule maintenance, and tell players when the server will be offline.
Version and platform compatibility
Nitrox’s available 1.8.0.0 release notes describe the project as ALPHA and explain that the Subnautica 2.0 game update required a major rewrite. Those notes state that players using Steam and Epic can use Nitrox with the latest Subnautica version supported by that release.
The same release information describes Linux support as experimental and macOS support as still pending for that release. Do not assume that a current console, Linux, or Mac installation can join simply because a Windows PC can host. Verify the compatibility statement for the exact Nitrox version and game build you intend to use.
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All players should update together. A launcher or game that is newer or older than the server can fail to connect, behave unpredictably, or load a world incorrectly. Keep a copy of the current installer and note the version before updating. If an update breaks a working session, stop the server, preserve its save data, and consult the release notes before changing more files.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Troubleshoot the common connection failures
Friends cannot see or reach the server
- Confirm that the Nitrox server window is still running.
- Verify that the friend is using the address shown by the server, not an obsolete address or the host’s private LAN address.
- Check that UDP port 11000 forwards to the current local IP of the host PC.
- Confirm firewall exceptions for
Subnautica.exeandNitroxServer-Subnautica.exe. - Restart the server after changing the router or firewall.
- Test whether the ISP uses carrier-grade NAT or whether two routers are creating a double-NAT path. If you cannot obtain a usable public route, try a VPN.
Local players connect but internet players do not
This pattern usually means the server itself works but the internet path is missing. Recheck the public address, UDP protocol selection, port-forward destination, and firewall profile. A local test does not prove that the router accepts unsolicited internet traffic. Test from a different connection rather than from another device on the same Wi-Fi.
The server starts, then players disconnect
Check whether the host computer is sleeping, losing its network connection, or being restarted by an update. Watch the server console for errors, confirm that everyone uses the same Nitrox and game versions, and avoid running a public session while troubleshooting. A smaller private test with the recommended five-player scale makes it easier to isolate a software or network problem.
UPnP does not open the port
Enable UPnP on the router only if you understand its security implications, then restart the router and Nitrox. If the mapping still does not appear, create the UDP 11000 rule manually. Carrier-grade NAT or an ISP-managed router can make both approaches impossible; a VPN or a separate managed server is the practical alternative.
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Make sure the same host machine and Nitrox installation are being used. Do not delete server data while experimenting with versions. Stop the server cleanly, preserve the existing save directory, and only then test a repaired or updated installation. Automatic saves help protect normal progress, but they are not a substitute for keeping a separate copy of important world data.
Public servers and reliability expectations
Nitrox does not host or moderate public servers. Public servers are operated by third parties, and Nitrox states that their uptime is not guaranteed. A listing that works today can disappear, change its rules, or be unavailable without notice. Ask the operator about moderation, backups, version support, and scheduled downtime before investing time in a shared world.
If dependable 24/7 access matters, keep a self-host machine available continuously or evaluate a separately verified managed host. Self-hosting gives you control over the files, password, settings, and update schedule, but you also carry responsibility for power, networking, backups, and troubleshooting.
Is a free Nitrox server worth it?
For a small group that already owns the PC game, self-hosting is the least expensive path: Nitrox costs nothing, and there is no required monthly server charge. The recommended five-player scale suits a private co-op session, and the server console, password protection, configurable settings, and automatic saves cover the essentials.
The trade-off is availability and administration. You must keep the host online, expose or virtualize the network path, maintain firewall rules, and keep versions aligned. Nitrox is an actively developed alpha project, so occasional compatibility or stability changes are part of using it. If those responsibilities are acceptable, install Nitrox and host locally. If you need a server that friends can enter at any time without depending on your home PC, compare a managed option using the criteria above rather than assuming that every public server provides reliable access.
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