How to Make a Calamity Mod Server for Terraria (2026)

To make a Calamity Mod server, run a tModLoader server (not vanilla Terraria), put CalamityMod.tmod and its required dependency CalamityModMusic.tmod in the server's Mods folder, list both in Mods/enabled.json, and start it. Friends join through tModLoader, which downloads the server's mods for them when they connect. Give it at least 4 GB of RAM, and 6 GB if you add more mods or have more than a handful of players.

Short answer

1. Install tModLoader on your PC, subscribe to Calamity Mod and Calamity Mod Music on the Workshop, and test them in a world.
2. In tModLoader, Workshop, Mod Packs, Save Enabled as New Mod Pack, then Open Mod Pack Folder.
3. Upload the .tmod files and enabled.json into the server's Mods folder.
4. Start the server as tModLoader and create (or upload) a world made with Calamity on.
5. Friends launch tModLoader, Multiplayer, Join via IP, and accept the mod download.

What Calamity needs

Calamity is a content mod for tModLoader, the free modding platform on Steam that everyone who owns Terraria can install. Vanilla Terraria cannot load it, and a vanilla or TShock server cannot run it.

Calamity Mod Music is a separate download because the soundtrack is big, but the current Calamity release declares it as a required mod. Leave it out and the server refuses to load Calamity, with an error about a missing CalamityModMusic. Put both on the server.

Everything else is optional. Popular companions are Boss Checklist, Recipe Browser, Magic Storage and Calamity's Vanities. Add them the same way, and check each mod page for its own dependencies.

Which tModLoader version?

Use the latest stable tModLoader on both server and clients. As of late 2026, stable tModLoader and Calamity are still on Terraria 1.4.4, while tModLoader's 1.4.5 port is in a beta branch. Do not run the beta for a Calamity server: Calamity is built for the stable branch, and players on the beta cannot join a stable server.

The tModLoader version has to match exactly between server and players. After a tModLoader update on Steam, update the server too. More in Terraria server version mismatch.

Step 1: Get the mod files

The easiest way to get exactly the right files is a mod pack from tModLoader on your PC:

1. Launch tModLoader. Open Workshop, Download Mods, and subscribe to Calamity Mod and Calamity Mod Music.
2. Go to Workshop, Manage Mods, enable both, and click Reload Mods.
3. Create a test world and play a minute. If it loads here, it will load on the server.
4. Go to Workshop, Mod Packs, click Save Enabled as New Mod Pack, name it, then Open Mod Pack Folder.

Inside you get a Mods folder with the .tmod files and an enabled.json, plus an install.txt with the Workshop IDs. The enabled.json for plain Calamity looks like this:

[
  "CalamityMod",
  "CalamityModMusic"
]

Only mods listed here load, even if other .tmod files sit in the folder. Names are the internal names, case sensitive.

Step 2: Put the mods on the server

Self hosted: copy the .tmod files and enabled.json into the Mods folder your tModLoader server uses, then start it with start-tModLoaderServer.bat (Windows) or ./start-tModLoaderServer.sh (Linux). On Linux, the manage-tModLoaderServer.sh script that ships with tModLoader can download Workshop mods listed in install.txt for you.

On GamezServers:

1. Set the server type to tModLoader in the panel and click Backup if there is a world you care about.
2. Stop the server.
3. Open the Files tab and upload the .tmod files and enabled.json into Mods. Calamity is a large file, so for slow uploads use SFTP: Settings, Show SFTP login, then FileZilla or WinSCP.
4. Start the server and watch the Console. You will see each mod load, then the world.

If the console stops on an error naming a mod, it is almost always a missing dependency or a mod built for a different tModLoader version.

Step 3: The world

Make the world with Calamity enabled. Calamity adds its own biomes, ores and structures during world generation, and a world made in vanilla is missing them.

• Let the server create it: set the world name, size and difficulty in the panel (or autocreate, worldname and difficulty in serverconfig.txt) and start. See Terraria server config explained.
• Upload one: create it in tModLoader with Calamity on, then upload both the .wld and the .twld file. The .twld holds all the modded data. Without it, modded blocks and items vanish. Steps in how to upload a Terraria world to a server.

Planning to play Calamity's harder Revengeance or Death modes? Make the world Expert or Master, because those modes build on top of Expert.

How much RAM does a Calamity server need?

Calamity is one of the heaviest Terraria mods. Loading it alone takes far more memory than a vanilla server ever uses, and boss fights with lots of projectiles add more.

Too little RAM shows up as very long start times, rubber banding during events and crashes on boss spawns. Our 6 GB Terraria plan is the one we would buy for Calamity, and you can move between plans from the dashboard, prorated, if you guessed low. See how much RAM a game server needs.

Step 4: How friends join

1. Launch tModLoader from Steam, not Terraria. Vanilla clients cannot join a modded server.
2. Multiplayer, Join via IP, pick a character, type the IP, then the port on the next screen.
3. tModLoader compares mods. If anything is missing or a different version, it offers to download the server's versions. Accept and let it reload.

Players do not need to subscribe to Calamity themselves. The server's mods are what count. Client side mods like UI or texture packs can stay enabled as long as they do not change gameplay.

Characters live on each player's PC, as in vanilla. Modded items only exist on characters played in tModLoader.

Updating Calamity

When Calamity updates on the Workshop, your friends' tModLoader updates it on their side, and they can no longer join a server running the old version. When that happens:

1. Backup the server.
2. Update the mods on your PC, make a new mod pack, and upload the new .tmod files over the old ones.
3. Restart and check the console.

Common problems

• "Missing mod: CalamityModMusic": upload CalamityModMusic.tmod and add it to enabled.json.
• Server ignores Calamity: the internal name in enabled.json is misspelled or the file is not in Mods.
• Kicked during mod sync: the server and client have different Calamity versions. Update the server's .tmod files.
• "You are not using the same version as this server": different tModLoader versions. Both should be on the latest stable (Steam, Properties, Betas, none selected).
• Crash on boss fights: memory. Move up a plan.

For more on modded Terraria servers in general, see how to add mods to a Terraria server.

The easy way

Running Calamity at home means keeping a PC on with 6 GB free just for the server and forwarding TCP 7777. On GamezServers you choose tModLoader in the panel, upload your mod pack, and the world stays online for the whole group with one click backups before every boss. Plans start at 2 GB, and the 6 GB plan is sized for Calamity: Terraria server hosting.

FAQ

Can I play Calamity on a TShock server?

No. TShock runs vanilla gameplay with admin tools and cannot load tModLoader mods. Calamity needs a tModLoader server.

Do my friends need to own tModLoader?

tModLoader is free on Steam for anyone who owns Terraria on PC. Each player installs it and joins through it.

Can console or mobile players join a Calamity server?

No. tModLoader only exists on PC, so only PC players with tModLoader can join a modded server.

Can I add Calamity to my existing world?

You can load it, and Calamity content that spawns over time will appear, but the ores, biomes and structures Calamity adds at world generation will be missing. For the full experience, start a new world with Calamity enabled.

Is Calamity Mod Music optional?

Not for the server. The current Calamity release lists it as a required mod, so both the server and players need it. tModLoader downloads it for players automatically when they join.