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How to Install Mods on a Terraria Server (tModLoader)

Switch your Terraria server to tModLoader and add Steam Workshop mods such as Calamity — the server downloads, updates and enables them on every restart.

How to Install Mods on a Terraria Server (tModLoader)

Terraria mods run on tModLoader, the official mod loader for Terraria. It is free on Steam for everyone who owns Terraria, and almost every mod — Calamity, Thorium, Magic Storage and thousands more — is published on its Steam Workshop.

On a Lobby Maker server you don't have to upload any mod files. You switch the server to tModLoader once, list the mods you want in one file, and restart: the server downloads every mod from the Steam Workshop, keeps them updated and turns them on by itself.

Make a backup first (Backups tab). Switching the server type reinstalls the server files, and a backup takes seconds to restore.

1. Switch the server to tModLoader

  1. Open your server in the panel (My game servers → Server Panel).
  2. Go to the Startup tab and pick tModLoader under Server Type.
  3. Confirm the reinstall and wait until it finishes.
  4. Start the server from the Console tab.

Your settings stay: tModLoader keeps the world name, size, difficulty, password and player limit you set on the Startup tab, and stores the modded part of a world in a .twld file next to it.

tModLoader runs on Terraria 1.4.4, one update behind Terraria Vanilla (1.4.5), and cannot open a world saved by 1.4.5. If your world is one of those, the server leaves it untouched and starts a separate modded world named after it, with -tmodloader at the end (world-tmodloader). Switch back to Terraria Vanilla and your old world is there again.

2. Find the mods you want

Browse the tModLoader Steam Workshop. Each mod's address ends with its Workshop ID: in https://steamcommunity.com/sharedfiles/filedetails/?id=2824688072 (Calamity Mod) it is 2824688072.

Check two things on each mod's page:

  • Required items — other mods it needs to work. Add those too.
  • The Both, Server or Client tag — where the mod runs. Mods tagged Client only change what one player sees (a different cursor, a UI tweak): every player installs those for themselves, and the server does not need them.

3. Add the mods

  1. Go to the Files tab and open mods/install.txt — or click Open mod list on the Mods tab.
  2. Add one mod per line — its Workshop ID or the whole Workshop link:
2824688072
https://steamcommunity.com/sharedfiles/filedetails/?id=2563309347
  1. Click Save Content, then Restart the server from the Console tab.

You can edit the list while the server runs: the server only reads it when it starts. On the start, the console shows each step: the mods being downloaded from the Steam Workshop, Enabled CalamityMod (Workshop 2824688072) for each new one, and the list of enabled mods. The first start with a big mod takes a few minutes — Calamity alone is about 400 MB.

Everything after a # is a comment. Use it to note what each ID is: 2824688072 # Calamity.

4. Join the server

Every player needs tModLoader from Steam, on the default (stable) branch. Players start tModLoader instead of Terraria and join through Multiplayer → Join via IP, as described in How to Join a Terraria Server.

When a player is missing a mod, tModLoader offers to download the server's mods as they join. If it doesn't, check that Download Mods From Servers is on in tModLoader's Settings, or subscribe to the mods on the Workshop.

Removing, disabling and updating mods

  • Remove or turn off a mod: delete its line from mods/install.txt, or put # in front of it, and restart. The server turns the mod off and deletes its download; adding the line back downloads it again.
  • The list is the switch: every mod in mods/install.txt is turned on at every start, even if tModLoader turned it off after an error. There is no need to edit mods/enabled.json for Workshop mods.
  • Updates: every restart updates the mods to their newest version on the Workshop. tModLoader itself updates on restart too, as long as tModLoader Version on the Startup tab is latest — which keeps the server on the same version as players who get tModLoader from Steam.

You can also upload your own .tmod files into the mods folder. Add the file name without .tmod to mods/enabled.json to turn it on.

Common problems

"Workshop item … has no tModLoader mod in it" in the console. The ID belongs to something else, or the download failed. Check the ID on the Workshop page and restart.

"Missing mod: SerousCommonLib required by MagicStorage" in the console. One of your mods needs another one, so tModLoader turned it off and started without it. Find the missing mod under Required items on the mod's Workshop page, add its ID to mods/install.txt and restart.

Players can't join: "version mismatch" or a list of different mods. Restart the server so it updates tModLoader and the mods, and ask players to restart tModLoader so Steam updates theirs. Both sides need the same versions.

The server is slow or runs out of memory. Big mods need RAM: plan on at least 4 GB for Calamity or a large mod list, and more for a big world with many players.

Frequently asked questions

Can I go back to vanilla Terraria? Yes: pick Terraria Vanilla under Server Type on the Startup tab. A world played with tModLoader loads without its modded parts, so make a backup before you switch. A vanilla world that tModLoader could not open is still there, unchanged.

Do I need a Steam account on the server? No. The server downloads Workshop mods anonymously.

Can I use mods from CurseForge? Download the .tmod file, upload it to the mods folder and add its name to mods/enabled.json. Mods from the Workshop are easier: they update by themselves.

Don't have a server yet? Rent a Terraria server on Lobby Maker — it is ready in about a minute, and switches to tModLoader in two clicks.