How to Host a Core Keeper Dedicated Server (2026 Guide)

To host a Core Keeper dedicated server, install the free Core Keeper Dedicated Server (SteamCMD app 1963720), run Launch.bat on Windows or _launch.sh on Linux, and share the Game ID it writes to GameID.txt. Players join with Join with Game ID, so no port forwarding is needed. A dedicated server takes up to 100 players, compared with 8 for a game hosted from the client.

Why use a dedicated server for Core Keeper?

Hosting from the game's main menu works, but the world only exists while the host plays and it stops at 8 players. A dedicated server fixes both:

The dedicated server is free, and nobody buys an extra copy for it. Every player needs their own copy of the game.

How do I install the Core Keeper server?

1. Install SteamCMD, or find Core Keeper Dedicated Server in your Steam library's Tools section.
2. Download the server files:

steamcmd +force_install_dir C:\CoreKeeperServer +login anonymous +app_update 1963720 validate +quit

On Linux, use a path like ~/corekeeper instead.

3. Start it with Launch.bat (Windows) or _launch.sh (Linux). The server runs without graphics and writes the Game ID to GameID.txt in the server folder once it is ready.
4. Send that Game ID to your friends.

Re-run the SteamCMD line after each game update so the server matches your players' version.

How does the Game ID join method work?

By default the server uses Steam's relay network. Players do not need your IP and you do not need to open ports, because Steam brokers the connection using the Game ID.

To join:

1. Launch Core Keeper and choose Join Game.
2. Pick Join with Game ID.
3. Paste the Game ID and connect.

The catch: if you do not set one, the server makes a new Game ID on every restart, and your friends' saved ID stops working. Set a fixed one with -gameid or in ServerConfig.json. The Core Keeper wiki's dedicated server page lists the rules: at least 28 letters and numbers, and it cannot contain Y, y, x, 0 or O. An invalid ID is replaced with a random one.

If you want players to connect by IP instead, start the server with -port. That switches it to Direct Connect mode, which the game uses for crossplay, and you then need to forward UDP 27015 and 27016. See how to port forward a game server if you go that route. Our how to join a Core Keeper dedicated server guide covers join problems in more detail.

What settings can a Core Keeper server change?

Settings can be passed as launch arguments or stored in ServerConfig.json, which sits with the world saves:

A Windows start line for a fixed, hard mode world:

CoreKeeperServer.exe -batchmode -world 0 -worldname "Deep Diggers" -worldmode 1 -maxplayers 12 -gameid <your-28-character-game-id>

Two things to know about world mode: it only applies when a world is created, and you cannot convert between Creative and non Creative worlds. Agree on Hard mode with your group before the first start, because enemies get much tougher.

Where are Core Keeper world files?

On a Windows server, saves default to:

%USERPROFILE%\AppData\LocalLow\Pugstorm\Core Keeper\DedicatedServer\worlds\

Each world is a single file named after its slot: 0.world.gzip, 1.world.gzip and so on. ServerConfig.json lives in the DedicatedServer folder above it.

To bring a world you started at home:

1. Find your world on your PC in the Core Keeper folder under AppData\LocalLow\Pugstorm\Core Keeper\, inside your Steam ID's worlds folder.
2. Stop the server and back up its worlds folder.
3. Copy your .world.gzip file into the server's worlds folder, renamed to the slot you want, for example 0.world.gzip.
4. Set -world (or world in the config) to that slot and start the server.

Can I run mods on a Core Keeper server?

Yes. Core Keeper mods are published on mod.io and built with the game's mod SDK. The server does not download them itself:

• Put the mods in the server's Mods folder and restart.
• Every player installs the exact same mods and versions from mod.io, since nothing syncs on join.
• On a Linux server, mods that add items or visuals only load if the author ships a Linux asset bundle. Script only mods usually work.

How much RAM does a Core Keeper server need?

Core Keeper is light. What grows over time is the explored map, so a world with several biomes dug out and large automated farms gets heavier.

For general sizing advice, see how much RAM a game server needs.

FAQ

How many players can join a Core Keeper dedicated server?

Up to 100, set with -maxplayers. A game hosted from the client is limited to 8.

Do I need to port forward for a Core Keeper server?

No, not with the default Game ID join. Port forwarding is only needed if you start the server with -port for Direct Connect.

Why does my Core Keeper Game ID keep changing?

The server makes a new one each start when no Game ID is set. Set a valid 28 character ID with -gameid or in ServerConfig.json.

Can I change an existing world to Hard mode?

World mode is set when the world is created. Start a new world slot with -worldmode 1 for Hard.

Do players need the same mods as the server?

Yes. Players must install the same mods and versions from mod.io, because the server does not send them on join.

The easy option: host it with GamezServers

Our Core Keeper server hosting runs the dedicated server for you and is ready minutes after you pay. The panel covers world name, world index, seed, max players up to 100, World Mode, auto update and a fixed Game ID, and you can copy the ID from GameID.txt in the file manager. Upload an existing world over SFTP and point the world index at it.

New customers get 50% off the first month, and friends can split the cost with each person paying their own share. Upgrade later if the cavern fills up.