How to Make a tModLoader Server

What tModLoader is, and the version catch

tModLoader is the standard way to play Terraria with mods on PC: a free, separate app on Steam that runs Terraria with mods from its own Steam Workshop. A tModLoader server is the same idea on the server side — it loads the mods, and every player connects with tModLoader too.

Two things trip people up:

• It is a different game for multiplayer purposes. tModLoader players cannot join a vanilla server, and vanilla players cannot join a tModLoader one. Everyone in the group runs tModLoader.
• It runs an older Terraria. Vanilla Terraria is on 1.4.5 (the "Bigger and Boulder" update of January 2026). tModLoader is still based on 1.4.4, and there is no 1.4.5 version of tModLoader yet. A world that has been played on 1.4.5 cannot be opened in tModLoader. The other direction works: a tModLoader world can be opened in vanilla 1.4.5, and is upgraded when it is.

So if you want a modded run, start the world in tModLoader. Do not take your vanilla 1.4.5 world to it.

Set up a tModLoader server at home

The quick way: host from the game

Install tModLoader from Steam (it is free, but you must own Terraria on Steam), enable your mods, then choose Multiplayer > Host & Play. Friends join through Steam. The world runs on your PC and stops when you quit.

A dedicated server on Windows or macOS

1. Get your mod list right in the game first. Subscribe to the mods on the Workshop and enable them in tModLoader. Then go to Workshop > Mod Packs, choose Save Enabled as New Mod Pack and Open Mod Pack Folder. You now have install.txt (the Workshop IDs) and enabled.json (which mods are on).
2. Start the server. In the tModLoader install folder (in Steam: right-click tModLoader > Manage > Browse local files), run start-tModLoaderServer.bat on Windows or start-tModLoaderServer.sh on macOS.
3. Answer the prompts: whether to use Steam, which world (or create one), max players, the port (7777 by default), port forwarding and a password.
4. Open the port. Forward TCP 7777 on your router to the PC, and friends join with your public IP through Join via IP.

Mods and worlds live in Documents/My Games/Terraria/tModLoader/ — Mods/ holds the .tmod files and enabled.json, Worlds/ holds each world as a .wld plus a .twld file with the modded data. Keep both files of a world together.

On Linux

tModLoader ships its own tools for this, called DedicatedServerUtils. Its documentation recommends running the server in Docker; the alternative is manage-tModLoaderServer.sh, which installs tModLoader (install-tml --github), downloads the Workshop mods listed in your install.txt (install-mods) and starts the server (start). Put install.txt and enabled.json in tModLoader/Mods/ and your world in tModLoader/Worlds/ first.

For the vanilla parts — the console, serverconfig.txt, port forwarding — see how to make a Terraria server; tModLoader accepts the same settings.

tModLoader server hosting on HytHost

1. Choose tModLoader at checkout. On Terraria hosting, pick a plan and select tModLoader as the server software. For Calamity or Thorium, start at Gold (6 GB).
2. Upload your mods. In the GamePanel file manager (or over sFTP), put the .tmod files in the mods/ folder. You find them on your PC in steamapps/workshop/content/1281930/, one folder per Workshop item.
3. Upload enabled.json into the same folder. It is a plain list of mod names, for example ["CalamityMod","CalamityModMusic"]; every mod you want switched on must be in it.
4. Restart the server and read the console: it lists each mod as it loads, and names the one that fails if one does.
5. Join. Friends open tModLoader, choose Join via IP and enter the address and port from your panel. Missing mods download from the server on the way in.

Already have a modded world? Upload the .wld and its .twld to the server's worlds folder, or send them to us and we migrate them free of charge. Nothing beyond tModLoader itself is preinstalled, so the mod versions are always the ones you chose.

Popular mod setups and how much RAM they need

Mods are the main thing that sets a tModLoader server's memory. Content mods add items, enemies, bosses and world generation, and all of it sits in memory whether anyone is using it or not. Neither tModLoader nor the big mods publish an official server figure, so the table below is our recommendation, sized with some headroom:

Two other things raise memory: world size (a large world takes roughly twice the memory of a small one before anyone joins) and players spread across the map. A vanilla server, for comparison, idles well under 1 GB on a small world.

To see which of your mods are heavy, turn on Show Mod Memory Estimates in tModLoader's settings. If the server crashes with OutOfMemoryException, it needs more RAM or fewer big mods — there is no setting that fixes it.

How friends get the mods

Friends do not have to collect the mod list by hand. When a tModLoader client joins, it compares its mods with the server's — name, version and file — and downloads anything missing or different directly from the server, then reloads and connects. Mods the client has that the server does not are switched off for that session. Mods marked as server-side only are never sent.

What each player needs:

• tModLoader itself, from Steam, on the same tModLoader version as the server.
• "Download Mods From Servers" left on in tModLoader's settings. It is on by default; with it off, the client refuses and lists the mods it would need.
• Trust in the server. tModLoader warns that mods can contain code and should only be downloaded from a host you trust. On your own server, that is you.

Common tModLoader server errors

"You are not using the same version as this server"

The tModLoader versions differ — they must match exactly. Steam updates players' tModLoader automatically, so after a tModLoader release, update the server too. The same message appears if you are accidentally connecting to a vanilla server on the same port.

A mod is missing or fails to load

Check that the mod is in enabled.json under its internal name (not its display name), that its dependencies are uploaded and enabled too, and that the .tmod file is the version your friends have. The server log names the mod that failed.

Out of memory

OutOfMemoryException in the log means the server ran out of RAM loading or running the mods. Remove a big mod, use a smaller world, or move to a larger plan.

The world will not open

Usually a world that was played on vanilla 1.4.5 — tModLoader cannot open it. It can also be a missing .twld file next to the .wld, or a mod the world depends on that is no longer enabled.

The game will not start after installing a "64 bit" mod

The old "tModLoader 64 bit" Workshop item is obsolete — current tModLoader is already 64-bit — and installing it stops the game launching. Unsubscribe from it.