Calamity Mod Server: Run Terraria Calamity on tModLoader

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Run a Terraria Calamity Mod server on tModLoader: the versions that match, both Workshop mods, enabled.json, world difficulty, server settings and RAM.

A painted Terraria landscape with tall round trees, a rope hanging into a cave, a bunny on the grass and a waterfall

Your group has finished vanilla Terraria and wants Calamity: 27 bosses, more than 2,400 items, the Rogue class and two difficulty modes above Expert, says its Workshop page, which had 9.9 million subscribers on 31 October 2026. A Calamity server is not a vanilla or TShock server with a plugin added. It runs on tModLoader, and the server and every player need the same mods at the same versions. This guide covers the matching versions, the setup, the world choices that are hard to undo and the RAM.

Quick answer: A Terraria Calamity Mod server runs on tModLoader's stable version, which is still built on Terraria 1.4.4, not on vanilla Terraria 1.4.5 or TShock. It needs two Workshop mods, Calamity Mod and Calamity Mod Music, because Calamity requires its soundtrack. Enable both on your PC, save them as a mod pack and copy the pack's install.txt and enabled.json into the server's Mods folder: tModLoader's server tools download the Workshop IDs in the first file and load the mods the second one lists. Generate a new world with Calamity enabled, on Expert for Revengeance or Master for Death, and plan 4 GB of RAM for Calamity alone with 4 to 8 players.

Which Versions a Calamity Server Runs

PartVersion on 31 October 2026Notes
tModLoaderv2026.08.3.0, the stable release of 1 October 2026Steam's default branch, built on Terraria 1.4.4.9 content
Calamity Mod2.2.3, the Workshop update of 9 August 2026Workshop ID 2824688072, 404 MB
Calamity Mod Music2.1Workshop ID 2824688266, 697 MB, required
Vanilla Calamity Mod Music2.1.3Workshop ID 2816188633, 910 MB, optional
Terraria (vanilla)1.4.5.8Not what tModLoader runs

Calamity's latest change note says version 2.2.2 was "published to Stable tModLoader v2026.6", and the official Calamity wiki lists the 9 August update as 2.2.3, a hotfix for a crash on multiplayer servers. Stable tModLoader releases, v2026.6 and v2026.08 included, all belong to the 1.4.4 line, which the tModLoader player guide calls "the stable version that we expect players to use". Keep the server there. The guide warns that "playing through the game on a preview version is not recommended", and the 1.4.5-dev beta is for testing the unfinished port to Terraria 1.4.5. A new stable release arrives on the first of each month; in Re-Logic's October 2026 State of the Game, the tModLoader team announced the next one for 1 November 2026.

Set Up the Calamity Mod Server

Step 1: Get Calamity Working on Your PC

tModLoader is a free app on Steam for Windows, macOS and Linux, and you need to own Terraria on Steam to install it. Then get the mods in one of two ways:

  • Steam Workshop: subscribe on the Calamity Mod page. It lists Calamity Mod Music under required items, and its description says the mod "REQUIRES Calamity's soundtrack", so subscribe to Calamity Mod Music too.
  • In tModLoader: open Workshop, then Download Mods, search for Calamity and download both.

Open Workshop, then Manage Mods, enable both and go back so tModLoader reloads. Start a single-player world once to check that everything loads.

Vanilla Calamity Mod Music is optional and replaces vanilla Terraria's music with Calamity compositions. Like the other two it is tagged "Mod Side: Both", so if you add it, the server and every player need it as well.

Step 2: Copy the Mod List to the Server

A server installs Workshop mods by ID, which is why tModLoader's server guide starts with a mod pack: "The steam workshop does not use mod names to identify mods".

  1. In tModLoader, open Workshop, then Mod Packs, and click Save Enabled as New Mod Pack.
  2. Click Open Mod Pack Folder, open the folder with your pack's name and then its Mods folder.

tModLoader writes install.txt there with the Workshop ID of every enabled Workshop mod, enabled.json with their internal names, tmlversion.txt with your tModLoader version and a copy of each .tmod file. For Calamity alone, the first two files hold these lines (the order can differ):

2824688072
2824688266

[
  "CalamityMod",
  "CalamityModMusic"
]

Copy both into the server's Mods folder. The README stresses: "You will need a Mods/enabled.json to contain all Mods that you want enabled". Players use the same pack; our tModLoader mismatch guide covers that side and what to check when someone cannot join.

Step 3: Start the Server

On your own Linux machine. tModLoader recommends its Docker setup, which brings SteamCMD along and installs the mods from install.txt each time the container starts. It needs an x86 machine: the README knows of no way to run tModLoader on ARM.

mkdir -p ~/calamity/tModLoader/Mods ~/calamity/tModLoader/Worlds
cd ~/calamity
curl -LO https://raw.githubusercontent.com/tModLoader/tModLoader/1.4.4/patches/tModLoader/Terraria/release_extras/DedicatedServerUtils/docker-compose.yml
curl -LO https://raw.githubusercontent.com/tModLoader/tModLoader/1.4.4/patches/tModLoader/Terraria/release_extras/DedicatedServerUtils/Dockerfile
# put install.txt and enabled.json in tModLoader/Mods
# and serverconfig.txt (below) in tModLoader
docker compose up -d
docker attach tml

The image runs as UID and GID 1000. If id shows other numbers, set them under the commented args in docker-compose.yml and chown -R the tModLoader folder to that user. Leave the console with Ctrl+P then Ctrl+Q; Ctrl+C stops the server. Without Docker, put tModLoader's manage-tModLoaderServer.sh in that tModLoader folder. It needs curl and unzip, plus SteamCMD on the PATH for the mods: ./manage-tModLoaderServer.sh install --github installs tModLoader (the version in Mods/tmlversion.txt, if you copied that file) and the mods, and ./manage-tModLoaderServer.sh start runs the server.

To let the server create its world without asking questions, put a serverconfig.txt next to Mods and Worlds:

world=/tModLoader/Worlds/Calamity.wld
autocreate=2
worldname=Calamity
difficulty=1
maxplayers=8
port=7777
password=change-me

With Docker, world must be the path inside the container, as above; with the script, use the full path to the file in your Worlds folder. autocreate=2 creates a medium world if the file does not exist yet (1 is small, 3 is large), and difficulty=1 is Expert; use 2 for Master. Players then join with the server's IP address and port 7777, the default.

On a rented server. On our Terraria hosting, tModLoader is a one-click switch in the panel, Workshop modpacks like Calamity install from there, and switching keeps your world files.

World Notes: Start a New World for Calamity

Generate it with Calamity loaded. Calamity places part of its content during world generation. Its Biomes page says the Sulphurous Sea "replaces the Ocean on world generation" on the Dungeon side, with the Abyss beneath it, and structures such as the Mechanic's Abandoned Shed spawn when the world is created. A world made without Calamity misses them.

Pick the world difficulty for the mode you want. Revengeance, which the wiki calls "the intended Calamity experience", needs an Expert or Master world. Death needs Master and is "not recommended for a first playthrough". A Classic world can use neither. You switch modes in the game, not in the config: open the inventory and click the Difficulty Indicator, below the map style buttons and left of the health bar, while no boss is alive. The wiki adds that Revengeance assumes you have finished vanilla Terraria at least once.

Moving a world you already play. A tModLoader world is two files: upload the .wld and the .twld, and point world= at the .wld. The tModLoader wiki stresses that it "must be .wld and not .twld". tModLoader does not use vanilla saves, and its team wrote in the February 2026 State of the Game that "Terraria players and worlds played on the 1.4.5 update can not be migrated to and used on current tModLoader".

Characters

Characters stay on each player's PC. tModLoader keeps its own player files apart from vanilla, with zipped backups in a Players\Backups folder (usage guide), and a character played in vanilla 1.4.5 cannot come along, for the reason above. Most groups start fresh. Every new character gets Calamity's Starter Bag, which holds starting weapons for each class, and in multiplayer it adds three Wormhole Potions.

Calamity's Server Settings

Calamity's server settings sit on the second page of its in-game config menu and in CalamityMod_CalamityServerConfig.json, per the wiki's configuration page. The wiki marks several defaults as what Calamity "is balanced around", so leave those alone. These four are worth a look for a group:

SettingRange and defaultWhat it does
PlayerRespawnTime_BossAliveSeconds: 15 to 60, default 15Respawn time while a boss is alive; otherwise players respawn in 3 seconds
BossHealthBoostPercent: 0 to 900, default 0Extra boss health on top of the multiplayer boost; bosses already spawned are not affected
TownNPCSpawnRateMultiplier1 to 10, default 1Faster town NPC respawns after a boss or event wipes out the town
BossesStopWeathertrue or false, default trueLate game bosses stop the rain; the wiki recommends it for performance problems in those fights

Set them in Calamity's config menu on your PC; tModLoader saves the file in its ModConfigs folder (Documents\My Games\Terraria\tModLoader\ModConfigs on Windows). Stop the server, copy the file into the server's ModConfigs folder next to Mods and Worlds, and start it again. Players who join get the server's values. Keep a copy: if the JSON does not parse, tModLoader's config code logs a warning, loads the defaults and deletes the file.

Updates, Backups and Crossplay

Calamity updates through the Workshop, tModLoader once a month, and both fix multiplayer problems: Calamity 2.2.3 fixed a crash on multiplayer servers, and the October tModLoader release fixed a multiplayer autosave crash and a network message issue that could stall servers. When an update lands:

  1. Stop the server with exit, which saves the world; exit-nosave does not (Official Terraria Wiki).
  2. Copy the .wld, the .twld and the ModConfigs folder off the server.
  3. Update the server. With Docker, run docker compose build --no-cache and then docker compose up -d; with the script, copy the new tmlversion.txt from a fresh mod pack if you use that file, then run ./manage-tModLoaderServer.sh install --github again.
  4. Start it, join once yourself, then tell your players which versions the server runs now.

The Calamity team announced version 2.3, the Anniversary update, in its June 2026 newsletter, with a reworked Desert Scourge that nests in the underground desert. It was not on the Workshop on 31 October 2026; read its notes before you update a world in progress.

Crossplay. Terraria 1.4.6, Crossplay Phase One, is meant to let console players join a game by typing in an IP address and port. On 29 October 2026 Re-Logic wrote that 1.4.6 was in final testing and not yet in submission. A Calamity server cannot follow: tModLoader runs only on Windows, macOS and Linux, its stable version is built on Terraria 1.4.4, and its port to 1.4.5 still has "many tasks to be done", the tModLoader team wrote in the same post. Console and mobile players cannot join a Calamity world. Do not open your Calamity world in vanilla Terraria to try crossplay; give that its own vanilla world. Our post on tModLoader and 1.4.5 has the background.

How Much RAM a Calamity Server Needs

Our Terraria RAM guide puts one heavy pack like Calamity at 4 GB for 4 to 8 players, and several heavy packs stacked, such as Calamity with Thorium, at 6 GB for 8 or more. Those are starting points, not measurements. tModLoader's usage FAQ names "large mods that add lots of items" as the main cause of out of memory errors, and its store page lists 6 GB of RAM as the minimum for a player's PC and 16 GB as recommended. To see what your pack weighs, turn on Show Mod Memory Estimates under Settings, tModLoader Settings, restart tModLoader and open the Mods menu: a graph at the top shows how much memory each mod uses.

Disk counts too: the Workshop lists Calamity Mod at 404 MB and Calamity Mod Music at 697 MB, about 1.1 GB together before worlds and backups. On our Terraria plans, Medium has 4 GB of RAM and 8 GB of storage for Calamity alone, and Large has 6 GB with 10 GB of storage for stacked packs.

FAQ

Where is the official Terraria Calamity wiki? At calamitymod.wiki.gg, which the Calamity team links as the official wiki from the Workshop page and calamitymod.com. It has boss guides, crafting trees, item pages and a changelog for every version.

Where can I find Terraria Calamity class setups? On the official wiki's Guide:Class setups, which lists gear for every class, the Rogue included, from before the first boss to the final bosses. Its header marks it as written for version 2.1.2, so check item pages for changes made in 2.2.

Does the server need Calamity Mod Music? Yes. Calamity lists it as a required item on the Workshop, its build file references CalamityModMusic, and both mods are tagged "Mod Side: Both", so the server and every player need it.

Can I add Calamity to an existing world? An older world does not get what Calamity places during world generation, such as the Sulphurous Sea and the Abyss beneath it. Start a new world with Calamity enabled and keep the old one as a separate save.

Does Calamity work on Terraria 1.4.5 or 1.4.6? No. tModLoader's stable version, which Calamity runs on, is still built on Terraria 1.4.4, and its 1.4.5 port is in beta. Console and mobile players cannot join, and 1.4.6 crossplay does not change that.

How much RAM does a Calamity server need? Plan 4 GB for Calamity alone with 4 to 8 players and 6 GB with other heavy mods and a bigger group, plus about 1.1 GB of disk for the two mods.

Sources

All opened on 31 October 2026: