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To play Core Keeper with friends, one player starts or loads a world, opens the pause menu, copies the in-game Game ID, and sends it to the group. Friends choose Join Game from the main menu and enter that ID. The host must remain in the world for a normal hosted session to continue.
How Core Keeper co-op works
Core Keeper’s standard multiplayer flow is online rather than local split-screen. One player runs the world session as host. Other players connect by entering the host’s Game ID, so there is no lobby browser or couch-co-op procedure to follow in the steps described by the official FAQ.
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The Game ID is displayed only after the host has entered the world. That means the host cannot simply copy an ID from the title screen, and friends cannot join until the host has started or loaded a world. The ID is the connection detail the group should share privately with the intended players.
Start a normal co-op game
Host: start or load the world
- Open Core Keeper.
- Select Start Game from the main menu.
- Create a new world or load an existing world.
- Wait until the game has placed you inside the world.
- Open the pause menu.
- Find the Game ID in the upper-left area of the pause screen.
- Use the copy option next to the ID, then send it to the friends you want to invite.
Copying the ID from the game is safer than retyping it. Send the copied value through a private message or group chat rather than posting it publicly. Anyone who receives the ID can try to use the join flow, so share it only with the people you intend to invite.
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- Build your underground paradise: Unleash your creativity and make your own way in Core Keeper. Create the ultimate foundation, from a cozy cottage to a bustling mining center, with a variety of materials and decorations. Customize your character's look to your playstyle and choose from a wide range of outfits and powerful armor pieces. In creative mode, experiment with unlimited resources and push the boundaries of building bases. Expand your experience even further with a thriving community and a wealth of player-created mods.
- Adventure awaits, solo or with friends: Embark on a solo adventure at your own pace, discover hidden secrets and build your dream base. Core Keeper also shines in seamless 2-4 player co-op. Collaborate, share resources, overcome challenges and create a shared world with your friends. Celebrate the changing seasons, trade with merchants, breed cute animal lovers, make music on playable instruments - the possibilities are endless. Do you want a dedicated world for your crew? Host your own server and discover at your leisure
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Friends: join with the Game ID
- Open Core Keeper and stay at the main menu.
- Select Join Game.
- Enter the Game ID supplied by the host.
- Confirm the join request and wait for the connection to complete.
If the host has not yet entered the world, ask them to finish loading first. The ID is useful only while the corresponding hosted session is available.
The host must stay in the world
A regular friend-hosted session depends on the player who started or loaded the world. The official FAQ’s host condition requires that player to remain in the world while friends play. If the host leaves the world, that condition is no longer met and the ordinary session cannot continue as though it were an always-on server.
Plan the session around the host’s availability. If the host needs to quit, warn the group before leaving and arrange another session later. Starting the same world again on another player’s device is a separate hosting arrangement; it does not turn the original session into a persistent shared server.
Platform compatibility and crossplay
The current official FAQ lists Core Keeper on PC through Steam, Epic, GOG, and the Microsoft Store, as well as Nintendo Switch, Nintendo Switch 2, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X|S. The crossplay rules differ between PC storefronts, console generations, and platform families.
| Players’ platforms | Compatibility described by the FAQ | What to check |
|---|---|---|
| PC on Steam, Epic, GOG, or Microsoft Store | PC storefronts can play together. | Make sure everyone is running a current compatible game version and uses the normal Game ID join flow. |
| PlayStation 4 and PlayStation 5 | Cross-generation play is supported within the PlayStation family. | Use the same hosted-session procedure and verify both installations are updated. |
| Xbox One and Xbox Series X|S | Cross-generation play is supported within the Xbox family. | Use the same hosted-session procedure and verify both installations are updated. |
| Different platform families, such as PC and PlayStation | Cross-platform play between platform families is not supported according to the FAQ. | Move the group to a compatible storefront or console family before troubleshooting IDs or network connections. |
| Nintendo Switch or Nintendo Switch 2 with another platform family | The FAQ lists the editions, but does not describe universal cross-platform play. | Check the current FAQ before planning a mixed-platform group. |
“Crossplay” should therefore not be treated as universal. PC storefront compatibility and same-family console cross-generation play are specifically described, while a PC-to-console or console-to-console-family session is not supported under the FAQ’s guidance. Platform support and rules can change, so consult the current official FAQ when organizing a group around a newly released edition or an updated build.
Check compatibility before troubleshooting
When somebody cannot connect, identify every player’s exact platform first. “PC” covers four storefronts that the FAQ treats as compatible, while “console” covers several families with different rules. A PlayStation 4 and PlayStation 5 pairing is not equivalent to a PlayStation and Xbox pairing. Likewise, owning the same game on two devices does not by itself establish cross-platform support.
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Use a dedicated server when the original host cannot be online
For an always-on arrangement, the official FAQ describes a Core Keeper Dedicated Server tool distributed through Steam. This changes the responsibility for keeping the session available: the dedicated-server process remains running while players connect with its Game ID, rather than requiring the original player to stay inside the game world.
This is a Steam-specific setup. The FAQ does not present it as public matchmaking, and it is not required for an ordinary evening of co-op. Use it when the group needs a server process that can remain running independently of a player’s normal game session.
Install and start the Steam tool
- Open Steam on the computer that will run the server.
- Open Steam’s Tools list, not just the regular game library.
- Find and install Core Keeper Dedicated Server.
- Launch the dedicated-server tool.
- Wait for the tool to display a Game ID.
- Leave the server process running while friends connect.
- Send the displayed Game ID to the players who should join.
- Each player opens Core Keeper, selects Join Game, and enters that server ID.
The server’s Game ID is separate from the ID shown by a player hosting directly from the game. Copy the value generated by the dedicated-server process and do not substitute an older ID from a previous run.
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What a dedicated server changes
The server does not eliminate the need for a host process; it moves that role from a player’s game client to a separate running tool. Someone still has to start the tool, keep the computer available, distribute the current ID, and stop the process when the group is finished. It is useful when the person who normally owns the world cannot stay in the game, but it is not a public matchmaking service that automatically finds players.
Choose the computer carefully. It must remain on and keep the dedicated-server process running for the period when friends need access. If that computer shuts down or the tool closes, players lose the same availability they would lose when a normal host leaves the world.
Stop the server safely
When the group is finished, stop the dedicated server through its command window. The FAQ’s command-window instruction is Windows-focused. If you are running the tool on another operating system, read the README included with the installed server before choosing a stop command or closing the process.
Check the README and version notes
Dedicated-server instructions are more version-sensitive than the basic Game ID procedure. Fireshine Games’ patch notes indicate that the dedicated-server README and multiplayer connection behavior have received updates. Before setting up a long-running server, open the README that came with the installed version and follow its current operating-system and launch guidance. Do not assume that a command or configuration detail from an older guide still applies.
Choose the right hosting method
| Question | Friend-hosted game | Steam dedicated server |
|---|---|---|
| Does the original host need to stay in the world? | Yes. The host must remain in the world for the ordinary session. | No, provided the dedicated-server process remains running. |
| Who keeps the session available? | The player who selected Start Game and loaded the world. | The computer and dedicated-server process running the Steam tool. |
| How do players connect? | They choose Join Game and enter the host’s in-game Game ID. | They choose Join Game and enter the ID generated by the server tool. |
| What equipment or account is required? | A normal Core Keeper installation on a supported, compatible platform. | A Steam installation with the dedicated-server tool installed, plus a computer that can keep the process running. |
| Best use case | A short session where one player is available to host. | A group that wants access without relying on the original player being inside the game. |
No maximum party size is established in the official material cited for this procedure. Do not infer a player limit from the number of people in your group; rely on the current game documentation for any capacity rule.
Troubleshoot a failed join
The Game ID is rejected or does nothing
- Ask the host to copy the ID again from the current pause menu. An ID copied from an earlier session may no longer point to the running world.
- Confirm that the host has reached the world rather than remaining at the main menu or loading screen.
- Have the joining player select Join Game from the main menu before entering the ID; the ID is not entered through the host’s Start Game path.
- Check that both players are on compatible platforms. A correctly entered ID cannot overcome unsupported cross-platform play between platform families.
- Close and reopen the game on the joining device if the menu appears stuck, then try the freshly copied ID once more.
A friend joined earlier but can no longer connect
- Verify that the host is still inside the world. Leaving the world ends the condition required for the ordinary hosted session.
- Ask the host whether the game was closed, the world was unloaded, or a new session was started. In each case, copy the current ID again.
- If the session uses a dedicated server, confirm that the server process is still running and that players are using the ID currently displayed by that process.
- Check for a game update on every device. Different versions can produce connection behavior that differs from the procedure documented for the current release.
Players are on different consoles or stores
First classify the combination before changing network settings. Steam, Epic, GOG, and Microsoft Store are treated as compatible PC storefronts in the FAQ. PlayStation 4 with PlayStation 5 and Xbox One with Xbox Series X|S are treated as same-family cross-generation combinations. A PC-to-console or one console family-to-another combination is not supported by the FAQ’s cross-platform guidance.
The dedicated server starts but friends cannot join
- Wait until the server tool has produced its Game ID; launching the program is not the same as completing startup.
- Send the ID generated by the running server, not the ID from a previous friend-hosted session.
- Keep the server process open while players connect.
- Read the installed version’s README for operating-system-specific startup and connection requirements.
- Check current Fireshine Games patch notes if the tool’s behavior or documentation appears different from an older setup guide.
The server will not stop cleanly
Use the server command window as described in the current README. The FAQ’s explicit command-window guidance is aimed at Windows, so do not copy a Windows command into a different operating system without checking the included documentation.
Plan a reliable co-op session
Before inviting anyone
- Agree on which platform family or PC storefront everyone will use.
- Choose the player who can remain in the world for the whole session, or decide in advance to run a dedicated server.
- Update the game on every participating device.
- Decide where the Game ID will be shared privately.
When the session begins
- The host starts or loads the world and waits until the character is inside it.
- The host opens the pause menu and copies the visible Game ID.
- Friends select Join Game and enter that newly copied ID.
- The host keeps the world open until everyone has finished.
When the group uses a dedicated server
- Install the Steam tool on the computer that will remain available.
- Start it before asking friends to connect.
- Distribute the ID only after it appears in the tool.
- Keep the process running for the duration of play.
- Stop it through the documented command-window method when the session is over.
Common questions about Core Keeper multiplayer
How do I start a multiplayer game?
Select Start Game, create or load a world, and wait until you are inside it. Open the pause menu, copy the Game ID shown near the upper-left, and send it to your friends. They join by selecting Join Game and entering that ID.
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How do I join a multiplayer game?
From the main menu, select Join Game and enter the ID supplied by the host. If the ID fails, confirm that the host is already in the world and has copied the current value from the pause menu.
Is Core Keeper couch co-op or split-screen?
The documented procedure is online multiplayer using a Game ID. The official FAQ focuses on online play and does not advertise a local split-screen or couch-co-op method.
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Can a host leave after friends join?
Not in a normal hosted session. The host must remain in the world while friends play. If the group needs access without that player in the game, use the Steam dedicated-server option and keep its process running.
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Is there cross-platform crossplay?
PC storefronts on Steam, Epic, GOG, and Microsoft Store can play together. PlayStation 4 and PlayStation 5 support cross-generation play, as do Xbox One and Xbox Series X|S. The FAQ does not support cross-platform play between different platform families, such as PC and PlayStation.
How do I host a Dedicated Server?
Install Core Keeper Dedicated Server from Steam’s Tools list, launch it, wait for a Game ID, and leave the process running. Give that ID to players, who enter it through Join Game. Stop the server through its command window and consult the installed README for current operating-system instructions.
How many players can join?
The official FAQ and patch-note material used for this guide do not establish a maximum player count. Do not rely on an unsourced number; check the current game documentation for any capacity limit.
Key points to remember
- Normal co-op is an online Game ID join process, not local split-screen.
- One player starts or loads the world and acts as host.
- Friends use Join Game and the host’s current Game ID.
- The host must stay in the world for a regular hosted session.
- PC storefronts can play together, and console cross-generation play is supported within PlayStation or Xbox families; cross-platform play between platform families is not supported in the FAQ.
- A Steam dedicated-server tool can provide a separate always-on host, but its README and version-specific instructions should be checked before setup.
Frequently Asked Questions
How do I start a multiplayer game in Core Keeper?
Choose Start Game, create or load a world, enter it, open the pause menu, and copy the Game ID. Send that ID to friends so they can use Join Game.
How do I join a Core Keeper game?
Choose Join Game from the main menu and enter the current Game ID from the host or dedicated-server tool.
Does Core Keeper support split-screen co-op?
The official FAQ documents online Game ID multiplayer and does not advertise local split-screen or couch co-op.
Can PC, PlayStation, and Xbox players play together?
PC storefronts can play together, and cross-generation play works within PlayStation or Xbox families. Cross-platform play between different platform families is not supported by the FAQ.
How do I host a Core Keeper Dedicated Server?
Install the dedicated-server tool from Steam’s Tools list, launch it, wait for its Game ID, keep it running, and have players enter that ID through Join Game. Follow the installed README for current stop and operating-system instructions.
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For a normal hosted world, the host must remain in the world. A dedicated server can keep the session available independently while its process remains running.
The Bottom Line
Start or load a world, copy its current Game ID from the pause menu, and have friends enter it through Join Game. Keep the host in the world for ordinary co-op. For a persistent setup, run the Steam Core Keeper Dedicated Server and follow its current README. PC storefronts and same-family console generations have specific compatibility, but cross-platform play between platform families is not supported.
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