To play Core Keeper with friends, one player starts or loads a world, opens the pause menu, chooses Copy game ID, and sends that ID to the group. Friends select Join Game and enter it. This normal session is available while the host remains in the world. If you need a world to stay available when that player is offline, install the official Core Keeper Dedicated Server, use its generated Game ID, and leave the server process running.
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Choose the multiplayer method that fits your group
Core Keeper has two official ways to play online. The first is a player-hosted world, which is the quickest option for a session you arrange together. The second is the dedicated-server application, intended for a persistent world that should not depend on one player launching the game and staying connected.
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Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →| Method | What you do | When it is available | Best for |
|---|---|---|---|
| Player-hosted game | Start or load a world, copy its Game ID, and send the ID to friends. | While the host is in the world. | A casual session or a group that plays at the same time. |
| Official Dedicated Server | Install the server from Steam Library > Tools, launch it, and share the generated Game ID. | While the server process is running. | A shared world that should be available without the usual player acting as host. |
The game does not publish a player-limit figure in the official material used for this guide, so do not rely on an unofficial number when planning your group.
How to invite friends to a normal Core Keeper world
The Game ID is the join key for a player-hosted online world. You do not create a conventional platform invitation from the steps documented by the developer; instead, you copy the ID shown in the game and send it through the chat your group already uses.
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- Launch the game as the host. From the main menu, choose Start Game.
- Create or load the world. Select an existing world or complete the world-creation flow, then enter it.
- Open the pause menu. On PC, the default key is Esc. If you changed your controls, use the key currently assigned to pause.
- Copy the identifier. Choose Copy game ID. The command places the world’s Game ID on your clipboard.
- Send the ID privately to your friends. Paste it into your group’s normal voice or text-chat service. Treat it as an access code for that session rather than posting it publicly.
- Have each friend join. A friend launches Core Keeper, selects Join Game on the main menu, and enters the Game ID.
- Keep the session active. The player-hosted world can be used by the group only while the host is in that world.
If the host leaves the world, friends should expect the player-hosted session to end or become unavailable. A dedicated server is the supported alternative when the group cannot coordinate around one person being present.
What the host needs to know
The host owns the running session
In a normal multiplayer game, the person who selects Start Game is both the world launcher and the active host. The world is not described in the official instructions as a continuously running service. Plan the play time around that person’s connection and availability.
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Copy the ID from the pause menu after loading the world you intend to play. If you switch to another world, have the group use the ID for that newly loaded world rather than assuming an earlier code applies.
Share the exact text
Game IDs are easy to mistype when copied manually. Use the in-game copy command, paste the result into chat, and ask friends to paste it into the Join Game field. Do not add spaces, punctuation, or explanatory characters inside the ID.
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How to join a friend’s game
- Open Core Keeper and wait for the main menu.
- Select Join Game.
- Paste or type the Game ID supplied by the host.
- Submit the ID and wait for the connection attempt to complete.
Joining does not replace the host’s need to remain in the world. If the code is correct but the host has not loaded the world, has left it, or has closed the game, there may be no active player-hosted session to enter.
When a dedicated server is the better choice
A dedicated server separates the running world from a normal player’s game client. This is useful when friends play at different times, when the person who created the world cannot attend every session, or when you want one machine to provide the always-available meeting point. The official application is called Core Keeper Dedicated Server.
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Set up the official Core Keeper Dedicated Server
- Open Steam. Go to Library and change the library filter so that tools are shown.
- Install the tool. Find Core Keeper Dedicated Server and install it from Steam Library > Tools.
- Launch the server. Start the installed server application. Allow it time to initialize.
- Read the generated Game ID. The running server displays a Game ID after startup. Copy that value exactly.
- Send the ID to the group. Friends use the ordinary game client, choose Join Game, and enter the server’s Game ID.
- Leave the process running. Keep the server window or background process open for the entire period in which the world must be available.
The server’s bundled README is part of the setup. Read the version installed on your machine before changing firewall or router settings, because network defaults and instructions can change between releases.
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Router access and ports for players outside your home network
The older official dedicated-server instructions identify UDP ports 27015–27016 as the default range and state that access from outside the local network requires forwarding those ports on a router with a public IP address. Those numbers are historical defaults, not a permanent guarantee for every current server build.
- Check the README bundled with the installed server before creating a forwarding rule.
- Forward the required UDP ports to the local machine running the server.
- Confirm that the router’s internet connection has a public IP; forwarding cannot make a private, carrier-grade NAT connection publicly reachable by itself.
- Allow the server application through the computer’s firewall when the operating system prompts you.
- Test from a friend’s connection outside the host’s home network instead of testing only from the same Wi-Fi.
Do not forward ports simply to fix a mistyped Game ID. First verify the code, the running process, and the server’s current README. Port forwarding is relevant to an externally reachable dedicated deployment, not to every local connection problem.
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Keep every dedicated-server installation on the same branch
The official instructions say that all players must use the same game branch. A branch mismatch can prevent a client from joining even when the Game ID and network configuration are correct.
- Check the branch selected for the game client on every computer.
- Check the branch used by the dedicated-server installation.
- Remove an experimental or beta selection if the rest of the group is on the standard branch, unless everyone intentionally uses the same alternative.
- After changing a branch, restart the game client and server before trying the Game ID again.
For cross-store dedicated servers, the August 2025 official update says that Steam, Epic, GOG, and Microsoft Store PC players can share a server when it is configured according to the server README. The README supplied with the current build takes precedence over older setup notes.
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Can Steam, Epic, GOG and Microsoft Store players play together?
Yes. The developer’s pinned FAQ says that players on different PC storefronts, including Steam, Epic, and GOG, can play together. The August 2025 update additionally names Microsoft Store PC players for shared dedicated-server use when the server follows its README configuration.
| PC arrangement | Officially supported? | Condition |
|---|---|---|
| Steam with Epic | Yes | Use the Game ID flow; keep versions and branches compatible. |
| Steam with GOG | Yes | Use the Game ID flow; keep versions and branches compatible. |
| Epic with GOG | Yes | Use the Game ID flow; keep versions and branches compatible. |
| Microsoft Store PC with other supported PC storefronts | Yes for the dedicated-server scenario described in the August 2025 update | Configure the server according to its bundled README. |
Can PC play with Xbox, PlayStation or Nintendo Switch?
No cross-platform crossplay is available according to the developer’s pinned FAQ. That means a PC player should not assume that a Game ID will connect to an Xbox, PlayStation, or Nintendo Switch player. The FAQ distinguishes this from cross-generation play and from cross-store PC play.
The FAQ lists availability on Steam, Epic, GOG, Microsoft Store, Nintendo Switch, Nintendo Switch 2, PlayStation 4, PlayStation 5, Xbox Series X|S, and Xbox One. Availability on a platform is not the same as cross-platform compatibility.
| Players’ platforms | What the current FAQ supports |
|---|---|
| Different PC storefronts | Supported, including Steam, Epic, and GOG; Microsoft Store PC is included for the dedicated-server arrangement described in the August 2025 update. |
| Different generations within a console family | The FAQ says cross-generation crossplay is supported. |
| PC with PlayStation | Not supported as cross-platform crossplay in the cited FAQ. |
| PC with Xbox | Not supported as cross-platform crossplay in the cited FAQ. |
| PC with Nintendo Switch | Not supported as cross-platform crossplay in the cited FAQ. |
| PlayStation with Xbox or Nintendo Switch | Not supported as cross-platform crossplay in the cited FAQ. |
Platform policies can change. Check the latest pinned developer FAQ before purchasing a copy specifically to play with someone on another system.
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Troubleshoot a friend who cannot join
“Join Game” cannot connect to a player-hosted world
- Ask the host to confirm that the world is currently loaded, not just visible in a menu.
- Request a freshly copied Game ID from the pause menu and paste it again.
- Confirm that both players are using supported platform groupings. A PC-to-console attempt will not be fixed by changing the ID.
- Check that both clients are on compatible versions and the same branch.
- Have the host restart the game, load the world, copy a new ID, and retry.
The dedicated server does not appear to be online
- Verify that Core Keeper Dedicated Server is still running and has finished startup.
- Use the Game ID generated by the server currently running, not an older code from a previous launch.
- Read the bundled README for the installed version and compare its required network settings with the router and firewall configuration.
- Check the branch on the server and every client.
- If friends are outside the local network, verify the required UDP forwarding and public-IP conditions.
Only local-network players can connect
This symptom points toward external reachability rather than the basic join procedure. Recheck the README’s port requirements, forward the current UDP ports to the server computer, and test from an outside connection. If the internet service uses carrier-grade NAT or another private-address arrangement, router forwarding alone may not provide an inbound path.
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Different PC storefronts are not automatically a problem. Verify that everyone is on a supported PC storefront, that the clients are updated consistently, and that the dedicated server is configured for cross-store use as described in the August 2025 update and the current README.
Practical group checklists
Before a one-night session
- Choose one player to launch the world.
- Confirm everyone is in the same supported platform grouping.
- Have the host load the intended world before sending the code.
- Copy the Game ID with Copy game ID, then paste it into the group chat.
- Keep the host in the world until everyone has finished playing.
Before moving to a dedicated server
- Decide which computer will stay on while the group plays.
- Install Core Keeper Dedicated Server from Steam’s Tools section.
- Read the included README for the installed version.
- Check branch selection on the server and clients.
- Configure firewall and, when necessary, router access using the current instructions rather than relying only on the older 27015–27016 defaults.
- Send the newly generated server Game ID to friends after startup.
Limits of what the official instructions establish
The cited official material explains the Game ID join process, the host-presence requirement, the dedicated-server route, platform availability, storefront compatibility, branch requirements, and historical port defaults. It does not establish a numeric player cap or document local split-screen support. Avoid promising either feature unless a newer official source confirms it.
The pinned cross-play FAQ is dated 23 March 2022, while the dedicated-server cross-store clarification is from August 2025. Because platform support and network behavior can change with updates, use the current in-game labels, the README installed with the server, and the latest developer FAQ when those sources differ from older instructions.
Quick Recap
Fast decision guide
- Everyone is on compatible PC storefronts and playing together now: use a player-hosted world and share its Game ID.
- The usual host cannot be online for every session: run the official Dedicated Server and share its generated Game ID.
- A PC player wants to join someone on Xbox, PlayStation, or Switch: do not purchase or troubleshoot on the assumption that cross-platform crossplay exists; the cited FAQ says it is unavailable.
- Friends are on Steam, Epic, GOG, or Microsoft Store PC: cross-store PC play is supported under the conditions described above.
- A server works locally but not for distant friends: inspect the current README, UDP forwarding, firewall permissions, public-IP status, and branch alignment.
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