RimWorld Open World Can't Connect or Mod Mismatch: How to Fix It

When players cannot join a RimWorld Open World server, work through four checks in order: everyone is on RimWorld 1.4 (not 1.5 or 1.6), the server's PlayerVersion matches the Open World client they installed, their mod list matches the server's enforced mods exactly, and they are on the whitelist if it is turned on. Those four cover nearly every failed join. If none of them is the problem, the server's port (TCP 25555 by default) is not reachable.

Keep in mind that Open World is abandoned. Nobody will patch the mod, so every fix below is a configuration fix. If your group keeps fighting it, RimWorld Together is the actively maintained alternative and runs on current RimWorld.

Check 1: RimWorld is on 1.4

Open World was built for RimWorld 1.4 and was never updated. On 1.5 or 1.6, the mod either does not load, throws red errors at startup, or the Open World button never appears on the main menu.

To switch:

1. In your Steam library, right click RimWorld and choose Properties.
2. Open Betas.
3. Pick the 1.4 branch from the dropdown.
4. Wait for Steam to download it, then launch.

The version shows in the bottom left of the main menu. Every player must do this. Back up newer saves before switching, because a 1.5 or 1.6 save will not load on 1.4.

Check 2: Harmony and load order

Open World depends on Harmony. Without it, the mod fails silently or logs errors as the game starts.

• Harmony must be enabled and sit at the very top of the mod list.
• Open World comes right after Harmony and the Core game.
• Restart RimWorld after any change to the mod list. Changes do not fully apply until a restart.

If the Open World button is missing after a restart, open the debug log (the error window that pops up, or Player.log in the RimWorld data folder) and look for Harmony or Open World errors.

Check 3: Player Version matches the client

The server only accepts one client version, set as PlayerVersion in Data/Config.json. A player on another version is refused, even if everything else is perfect. This catches groups out when one person installed the mod from the Workshop and another grabbed a release from GitHub.

1. Find the version of the Open World client your group uses (shown in the mod's description or its folder).
2. Set PlayerVersion to exactly that number, for example 1.2.
3. Restart the server.
4. Make sure every player has the same client version.

Check 4: Mods match the server

This is the classic Open World failure, and it shows up in two ways: a refused login, or a successful login followed by desyncs, errors and broken trades.

With EnforceMods on, a player must load exactly the mods in the server's enforced mods folder. Missing mods, extra mods and a different order can all cause trouble.

1. Look in the enforced mods folder on the server and list every mod in it.
2. Share that list with players, in order, ideally as a Steam Workshop collection.
3. Players disable everything else, enable the list, and restart.

With UseModBlacklist on, any mod in the blacklist folder blocks the player. Ask them to disable it, or remove it from the blacklist if it is harmless.

With both off, players can join with anything. That is how a server ends up with desyncs that look random: two players with different mods affecting the same trade or caravan. Switch to an enforced list once you see it.

Mods that change world generation are a special case. They need to be present when the world is created. Adding one later can break the planet for everyone, and the fix is usually a fresh world.

Check 5: Whitelist and accounts

With UseWhitelist on, only usernames in the whitelist file can join. The name must match the Open World username the player registered, not their Steam name. Add it, save the file and restart the server.

Players also need the same username and password every time. A player who forgets their password can be helped from the console: version 1.0.4 added a change password command, and help lists the exact name in your build.

If version 1.0.4's optional server password is set, players must enter it too.

Check 6: The connection itself

If the game says it cannot reach the server at all:

• The default port is TCP 25555. Check ServerPort in Config.json.
• Forward the port as TCP on a home router and allow it through the firewall. Our port forwarding guide has the steps.
• Players type the address and the port. A wrong port is easy to miss.
• Make sure the server window shows it is listening and did not crash on start. On Linux and in containers, a missing .NET Core 3.1 runtime stops it immediately.

Problems after joining

Fixing it on a hosted server

On a GamezServers Open World server, Player Version, Enforce Mods, Use Mod Blacklist, Use Whitelist and Use Custom Difficulty are panel settings, so you change them there and restart instead of editing Config.json. The panel writes them into the config on every start. The mod folders and the whitelist file are in the file manager, and the port is set for you, so check 6 mostly goes away. Take a one click backup before changing mods on a running planet. If your group decides to move on, the same server can switch to RimWorld Together from the panel, and our comparison of the two explains what changes.

FAQ

Why is the Open World button missing from my main menu?

RimWorld is not on 1.4, Harmony is missing or not at the top, or the game was not restarted after enabling the mod.

What should Player Version be set to?

The exact version of the Open World client your players installed. A mismatch refuses everyone on another version.

Can players join with different mods?

Only if Enforce Mods is off. It works, but different mods are the main cause of desyncs, so an enforced list is safer.

Does Open World work with RimWorld 1.6?

No. The mod is abandoned and only supports 1.4.

What port does Open World use?

TCP 25555 by default, set as ServerPort in Config.json.