Transfer a Core Keeper World and Enable Crossplay

Back up, then compare the folders

On the game's main menu, CTRL ALT B writes an archive to the desktop:

%userprofile%\Desktop\CoreKeeperSaves.zip

The wiki tells you to have that before you post a Game ID in public. Open the archive. It is not a copy of the dedicated-server folder, which is outside the player's Steam profile.

Client worlds:

%APPDATA%\..\LocalLow\Pugstorm\Core Keeper\Steam\<SteamID>\worlds\

Dedicated-server worlds:

%APPDATA%\..\LocalLow\Pugstorm\Core Keeper\DedicatedServer\worlds\

Dedicated config is ServerConfig.json in that DedicatedServer folder. The server worlds folder can be missing until the first save, about 30 seconds after a player logs in. You can create the folder and paste worlds into it.

Stop the server with Q in the PowerShell window the wiki describes. Do not kill the process. Copy both worlds folders aside. Only then paste the client save into the dedicated worlds folder.

The wiki does not name the file extension. Create a test world on the server, compare filenames with the client, and replace the matching slot instead of mixing two indexes. -world selects the slot. The range and the default are in ARGUMENTS.txt next to the server. Read that file again after 1.3.

Start it and recognize the world

Leave the client copy intact. Start the dedicated server, wait for a save, and join with the Game ID (GameID.txt beside the executable on builds that write it). You should recognize a landmark from the client world. Place a block, quit with Q, start again, and confirm the block is still there.

A new world means another index, a worlds folder that is not under the Windows account running the server, or a copy taken while the process was still writing. Restore the zip and the dedicated folder from before the paste.

Crossplay is not on the public setup page

Pugstorm's Steam post describes shared sessions across Steam, Epic, GOG and the Microsoft Store. The setup wiki does not give the switch. The dedicated-server README, as carried by projects that ship it, asks for three things before direct connections work: open the port on the firewall, forward it, and pass it at launch with -port. Steam players can still use the Game ID. Everyone else types an IP, a port and a password.

-allowonlyplatform limits joins to one store (Steam, Epic, Microsoft or GOG in those README copies) and turns crossplay off. It does nothing unless -port is set. Public copies of ARGUMENTS.txt also say -port and -ip are read from the command line and ignored in ServerConfig.json. If your local file disagrees, follow the file.

Without -port, the server stays on the Steam relay: no forward, and no direct join for the other PC stores. The direct-connect password is not the Game ID. Do not publish the Game ID without the backup the wiki asks for.

The rest of the switches are in the launch arguments guide. Offers: Core Keeper comparison.

Questions