How to Host a FOUNDRY Dedicated Server (2026 Guide)

To host a FOUNDRY server, install FOUNDRY: Dedicated Server (SteamCMD app 2915550, Windows), put an App.cfg file next to FoundryDedicatedServer.exe and set server_name, server_password, server_world_name and server_max_players. Open UDP 3724 for the game and UDP 27015 for the Steam browser, then start FoundryDedicatedServerLauncher.bat. Friends join with Multiplayer > IP Direct Connect. The world name is also the save folder name, so keep it the same forever.

Why run a dedicated FOUNDRY server?

In a hosted co-op game, the factory only exists while the host plays. A dedicated server keeps the world available to everyone, research is shared by everyone on it, and one person's PC no longer simulates every conveyor and train for the group. The developers designed multiplayer mostly for 2 to 4 players, with no hard limit, according to the Paradox FAQ, so most servers are small crews.

What do you need to run a FOUNDRY server?

The server is a 64 bit Windows program. On Linux it runs under Wine, which is how most hosts run it. Memory grows with the size of the factory and how much voxel terrain players have dug out.

A fast CPU core matters as much as RAM once the factory gets big, because the server simulates every machine and belt.

How do I install the FOUNDRY dedicated server?

1. Install it from Steam: in your Library, tick Tools in the filter and install FOUNDRY: Dedicated Server. Or use SteamCMD:

steamcmd +@sSteamCmdForcePlatformType windows +force_install_dir C:\FoundryServer +login anonymous +app_update 2915550 validate +quit

2. Create App.cfg in the same folder as FoundryDedicatedServer.exe. The developers host an example App.cfg you can start from.
3. Run FoundryDedicatedServerLauncher.bat, or start the server from your Steam Library.
4. Leave it running. Stop it with Ctrl+C in the console so it saves cleanly.

Keep the server on the same game version as your players. When FOUNDRY updates on Steam, update the server too, or nobody can connect.

What goes in App.cfg?

App.cfg is plain key=value lines, one per line. A typical friends server:

server_name=Iron Belt Co-op
server_password=conveyor42
server_world_name=IronBelt
server_max_players=8
server_is_public=false
pause_server_when_empty=true
autosave_interval=300
server_port=3724
server_query_port=27015
mapseed=42938743982

Every key from the official dedicated server page:

Two things catch people out:

• The seed key is mapseed, with no underscore. A line like map_seed= is not in the official list, so the server ignores it and you get the default seed. The seed only matters before the world exists.
• server_world_name picks the save folder. Change it and the server starts a brand new world in a new folder. Your old factory is still on disk, just not loaded.

Where does the server keep the world?

By default, saves go to:

C:\Users\<you>\AppData\LocalLow\Channel 3 Entertainment\FoundryDedicatedServer\save\<server_world_name>\

If you set server_persistent_data_override_folder, saves and logs go there instead, which is how hosts run several servers on one machine. Back up the whole world folder before game updates and before installing or removing mods.

What ports does a FOUNDRY server use?

Forward both on your router and allow them through Windows Firewall. If you run a second server, give it a new pair in its own App.cfg. Our port forwarding guide covers the router side.

How do players join a FOUNDRY server?

1. Launch FOUNDRY and click Multiplayer.
2. Choose IP Direct Connect.
3. Enter the server's IP and port, for example 203.0.113.10:3724, and the password.

A public server also shows in the Steam server browser, but only with server_is_public=true and the query port open. Direct connect always works, so use it for the first join.

How do mods work on a dedicated server?

FOUNDRY has Steam Workshop support, and most mods are built on the Unfoundry framework. Popular ones include Duplicationer (blueprints), Tweakificator and PlanIt.

• Put the server copies in the server's Mods folder and restart.
• Install Unfoundry on the server first if a mod depends on it.
• Mods do not sync when players join. Make a Steam Workshop collection with the server's exact mod list and have everyone subscribe.
• Some mods are client only. Check each mod page for dedicated server support before adding it.

Back up the world before adding a mod that adds blocks or machines, since removing it later can leave a world that will not load.

Moving an existing world onto it

You can keep playing the world you started in single player or hosted co-op. In the game, open Load Game and click Open SaveGame Folder to find it. Stop the server, copy the world folder into the server's save folder, and set server_world_name to the folder's exact name, or rename the folder to match. Start the server and check the console. Step by step: how to move a FOUNDRY world to a dedicated server.

Common problems

• Server makes a fresh world: server_world_name does not match the folder name in save, letter for letter.
• Not in the server browser: server_is_public is false or UDP 27015 is closed. Use IP Direct Connect.
• Friends time out: UDP 3724 is not forwarded, or it is forwarded as TCP.
• "Version mismatch" or cannot join after a patch: update the server to the same build as the game.
• A mod fails to load: Unfoundry is missing on the server, or the mod is client only.

The easy option: host it with GamezServers

Our FOUNDRY server hosting runs the dedicated server for you. On our servers the Settings page writes the name, password, world name, max players, public listing, pause when empty and autosave interval into App.cfg every time the server starts, so change those in Settings rather than in the file, or your edit is replaced on the next start. Saves sit in serverfiles/save/, and SFTP or the file manager handles uploading a world and the Mods folder.

New customers get 50% off the first month on monthly plans, friends can split the bill with each paying their own share, and you can move up a plan as the factory grows without losing the world.

FAQ

What ports does a FOUNDRY dedicated server need?

UDP 3724 for the game and UDP 27015 for the Steam server browser. The query port is only used when the server is public.

Where are FOUNDRY dedicated server saves stored?

In AppData\LocalLow\Channel 3 Entertainment\FoundryDedicatedServer\save\ under a folder named after server_world_name, unless you set a data override folder.

How many players can join a FOUNDRY server?

You set the cap with server_max_players. The game is designed mostly for 2 to 4 players per server, but there is no hard limit.

Why did my server start a new world?

The world name changed or does not match the save folder. Set server_world_name back to the old folder's exact name and restart.

Do players need the same mods as the server?

Yes. Mods do not download on join, so share a Workshop collection with the server's mod list.