Core KeeperHow to Join a Core Keeper Dedicated Server (Game ID or IP)
Join a Core Keeper dedicated server with its Game ID or by IP: where to find the ID, the menu steps, and fixes for wrong IDs, version mismatches and mods.
Updated Oct 3, 2026 · 6 min read
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To join a Core Keeper dedicated server, open Core Keeper, click Join Game, paste the server's Game ID into Join with Game ID and connect. The Game ID is printed in the server console at startup and saved in GameID.txt next to the server files. If the server runs in direct connect mode, open the dropdown next to Join with Game ID, pick Join with IP and enter the IP, port and password instead.
What is a Core Keeper Game ID?
Core Keeper does not use a server browser. A dedicated server has a Game ID, a long string of letters and numbers that works like an invite code. When players join with it, the connection goes through Steam's relay network (Steam Datagram Relay), so the host does not need to open any ports and the server's real IP stays hidden.
The server makes a new Game ID each time it starts unless you give it a fixed one. That is why friends' saved IDs suddenly stop working after a restart. Setting a fixed ID (the -gameid launch option, or the Game ID field in our panel) keeps it the same forever.
Where do I find the Game ID?
Any of these works:
- The console. After the server finishes loading the world, it prints the Game ID.
GameID.txt. The server writes the current ID to this file next to its executable. Open it in the file manager.- Your panel setting. If you set a fixed Game ID, that is the ID.
Copy and paste it rather than typing it. Game IDs are long, and one wrong character gives a plain "could not connect" with no hint why.
How do I join with a Game ID?
- Launch Core Keeper and pick your character.
- Click Join Game.
- Make sure Join with Game ID is selected.
- Paste the Game ID and click Join.
There is no password step for Game ID joins. Anyone with the ID can get in, so treat it like a password and share it only with your group. If it leaks, change it to a new fixed ID and restart.
How do I join by IP (direct connect)?
Core Keeper dedicated servers also have a second network mode. When the server is started with a -port, it switches from Steam relay to direct connections:
- Click Join Game.
- Open the dropdown arrow next to Join with Game ID and choose Join with IP.
- Enter the server's IP address, port and password.
- Click Join.
Direct connect matters for two reasons. It is the mode that allows crossplay, because Game ID joins only work for Steam players, and some players find it more stable than the relay. The trade off is that the port has to be reachable from the internet, and the IP is visible to players. The password is required in this mode: if the host does not set one (up to 28 characters), the server generates a random one, which is shown in the console.
| Join with Game ID | Join with IP | |
|---|---|---|
| How the server runs | Default, no -port |
Started with -port |
| Port forwarding | Not needed | Needed on a home server |
| Crossplay | Steam only | Steam, Epic, Microsoft Store and GOG |
| Password | None, the ID is the secret | Required |
| Server IP visible | No | Yes |
A direct connect server can also be limited to one store with -allowonlyplatform (1 Steam, 2 Epic, 3 Microsoft, 4 GOG).
Why can't I join my Core Keeper server?
| Problem | What is happening | Fix |
|---|---|---|
| "Could not connect" with a Game ID | The ID is wrong or changed on restart | Copy the current ID from GameID.txt or the console, then set a fixed one |
| Worked yesterday, not today | The game updated and the server did not | Restart the server so it updates, and make sure everyone runs the latest game version |
| Friend on Game Pass or Epic cannot join | Game ID joins are Steam only | Run the server in direct connect mode and join by IP |
| Kicked or errors right after joining a modded server | Mods do not match | Everyone needs the same mods and versions as the server's Mods folder |
| "Server is full" | Max players reached | Raise the player cap (up to 100 on a dedicated server) and restart |
| Direct connect times out | Port not reachable | Forward the UDP port on a home server, or use the Game ID |
| Wrong password | Random password generated | Read it from the console, or set your own |
| Joined an empty, unfamiliar world | Server loaded a different world index | Check the world index setting points at your save |
Updates
Core Keeper clients and servers must run the same version. After a patch, players update through their launcher (the Steam version updates itself), so the server is usually the one behind. A dedicated server with auto update installs the new build on its next restart. If the group is mid session when an update drops, restart the server once everyone has updated.
Mods
Core Keeper mods come from mod.io and are built with the game's official mod SDK. The server does not send mods to players: each player installs the same mods, in the same versions, from mod.io. Script only mods usually work on a server. Mods that add items or art need a Linux build from their author to load on a Linux server.
How many players can join?
Up to 100 on a dedicated server, set with the max players option. A world hosted from the game client stops at 8, which is the main reason bigger groups use a dedicated server. See how to host a Core Keeper server for the full setup.
FAQ
How do I find my Core Keeper server's Game ID?
Read it from the server console after the world loads, or open GameID.txt in the server folder. On our servers you can also set your own fixed Game ID in the panel.
Why does my Core Keeper Game ID keep changing?
The server generates a new one at every start unless a fixed Game ID is set. Set one with the -gameid option or the panel's Game ID field.
Do I need to port forward to join a Core Keeper server?
Not for Game ID joins, which use Steam's relay. Direct IP joins need the server's UDP port to be reachable.
Can Xbox Game Pass players join a Core Keeper dedicated server?
Only in direct connect mode, joining by IP. Game ID joins work for Steam players only.
Does a Core Keeper server have a password?
Game ID joins have no password, so keep the ID private. Direct connect mode always uses a password.
The easy way to keep the ID stable
On a GamezServers Core Keeper server, you set a fixed Game ID in the panel once and your friends' saved ID keeps working through restarts and updates. Auto update keeps the server on the version players run, mods go in the Mods folder through the file manager, and the world stays online when you log off. Plans start at 4 GB, enough for a group of up to eight.
Skip the setup. Your own Core Keeper server.
Then $9.99/mo. Just trying it? $2.50 for 3 days