How to Set Up a tModLoader Server (Calamity, Thorium & More)

tModLoader turns Terraria from a complete game into a platform. Calamity adds boss fights that make Moon Lord feel like a tutorial. Thorium builds out entire new class fantasies. Fargo’s Souls adds difficulty layers that’ll make you question your life choices. And that’s just the content mods - there are hundreds of quality-of-life improvements that smooth out everything from crafting to inventory management.

Running a tModLoader server isn’t complicated, but there are a few things that trip people up. This guide covers the setup process, the 32-bit vs 64-bit decision, and how to troubleshoot the issues that actually come up.

What you need to know first

tModLoader is a separate application from vanilla Terraria. On Steam, it’s listed as its own entry - search “tModLoader” in your library (you may need to enable “Tools” in the dropdown filter). It’s free if you own Terraria.

The server and all players need to be running the same mods on the same versions. This is the most common source of connection issues - someone has an outdated mod or is missing one entirely. We’ll cover how to handle this later.

The 32-bit vs 64-bit question

tModLoader historically ran as 32-bit, which caps memory usage at 4GB. This matters if you’re self-hosting or using a provider that defaults to 32-bit builds.

WinterNode runs 64-bit tModLoader by default, so this ceiling isn’t something you’ll hit with us. But it’s useful context - if you’re comparing notes with friends on other hosts or see forum posts about the 4GB limit, that’s what they’re talking about.

The 64-bit version runs a bit heavier at baseline, and occasionally you’ll run into mod compatibility quirks depending on what you’re installing. Most popular mods (Calamity, Thorium, etc.) work fine. If you’re using something more obscure, it’s worth checking the mod’s page for compatibility notes.

To check what a server is running, look at the tModLoader startup logs - it’ll indicate 32-bit or 64-bit in the version info.

Setting up your server

When you order a Terraria server from WinterNode, you can select tModLoader as your server software on the order form. If you started with vanilla and want to switch, open a support ticket and we’ll handle the conversion.

Once your server is running tModLoader, here’s the mod installation process:

Step 1: Decide on your mod list

Before touching the server, figure out what you’re running. The easiest approach is to set up tModLoader on your local game first:

1. Launch tModLoader from Steam
2. Go to Workshop > Download Mods
3. Search for and subscribe to the mods you want
4. Enable them in the Mods menu
5. Launch a test world to make sure everything loads

Write down your final mod list and versions. You’ll need this for the server.

Step 2: Install mods on the server

The next step is to install the mods on your server. To do this, you first need to locate the mod files:

1. After subscribing to the mods on the Steam workshop, navigate to Documents/My Games/Terraria/tModLoader/Mods on your PC. This is typically where mod files are located (may vary depending on your game’s install location)
2. Inside that folder, you’ll find various numerical folders. Each of these is a mod. You’ll see folders within those folders such as 2024.5, 2025.9, etc. Enter the newest directory, and you’ll see the .tmod file, which you’ll need to upload to the server.
3. Upload the .tmod files to your server’s mods folder via the file manager or SFTP

Step 3: Configure enabled mods

Having mod files on the server isn’t enough - you need to tell tModLoader which ones to actually load. This is handled through enabled.json in the Mods folder.

The file is a simple JSON list of mod names:

[
  "CalamityMod",
  "ThoriumMod",
  "RecipeBrowser",
  "BossChecklist"
]

Make sure mod names match exactly - they’re case-sensitive.

Step 4: Generate or upload your world

Content mods like Calamity add their own biomes, structures, and ore distributions. These generate when the world is created, not retroactively. For the best experience, create a fresh world after installing content mods.

You can either:

• Let the server generate a new world on first startup
• Create a world locally with your mods enabled, then upload the world files to the server

If you’re uploading: world files are in Documents/My Games/Terraria/tModLoader/Worlds. You need both the .wld file and the .twld file (tModLoader’s extra world data).

Step 5: Test the connection

Have everyone install the same mods locally:

1. Subscribe to the same Workshop mods (or install the same .tmod files)
2. Enable the same mods in the same order
3. Launch tModLoader and connect to the server

If someone gets stuck on “Downloading mods from server,” check their mod versions against the server’s. Even minor version mismatches can cause issues.

Popular mod combinations

These setups are common among our customers and known to work well together:

Calamity playthrough (4GB recommended)

• Calamity Mod
• Calamity Mod Music
• Boss Checklist
• Recipe Browser
• Magic Storage

This is the “standard” Calamity experience. Music mod is technically optional but the soundtrack is worth it.

Thorium playthrough (3-4GB)

• Thorium Mod
• Boss Checklist
• Recipe Browser
• Fargo’s Mutant Mod (just the helpful NPCs, not the souls content)

Thorium feels more like a Terraria expansion than an overhaul. Integrates well with vanilla progression.

Kitchen sink modded (6GB+)

• Calamity Mod
• Thorium Mod
• Fargo’s Souls Mod
• Stars Above
• Boss Checklist
• Recipe Browser
• Magic Storage
• Various QoL mods

This is “I want everything” territory. Expect longer load times and some progression confusion as different mods’ content overlaps. We’ve seen these setups start comfortable at 4GB but hit memory pressure after extended sessions with lots of world exploration - 6GB gives you headroom. Fun chaos, but maybe not for first-time modded playthroughs.

Server-side vs client-side mods

Not every mod needs to be on the server. Understanding the difference saves headaches:

Server-side (must match):

• Content mods (Calamity, Thorium, etc.)
• Mods that add items, NPCs, or change world generation
• Mods that affect gameplay mechanics

Client-side only (players can have different setups):

• Minimap mods
• UI improvements
• Visual-only changes like health bar mods
• Some quality-of-life mods (check the mod’s description)

Client-side mods don’t need to be on the server, and players can use different ones without causing mismatches.

Troubleshooting common issues

“Mod version mismatch” on connect

Someone has a different version of a mod than the server. Have everyone:

1. Unsubscribe from all mods
2. Close and reopen tModLoader
3. Subscribe to the exact same Workshop items
4. Try connecting again

Server crashes on startup

Check the server logs for the specific error. Common causes:

• Mod conflicts (two mods trying to change the same thing)
• Missing dependencies (some mods require other mods)
• Incompatible mod versions
• Out of memory (see the 32-bit ceiling issue)

Try disabling mods one at a time to isolate the problem.

“Out of memory” errors

If you’re on a 32-bit tModLoader build (not WinterNode - we run 64-bit), you’ve hit the 4GB ceiling. Options:

• Remove some mods
• Switch to 64-bit tModLoader
• Reduce world size

If you’re on 64-bit and still hitting memory limits, you may need a server with more RAM. Heavy mod stacks (Calamity + Thorium + extras) can push into the 6GB+ range after extended play sessions.

World doesn’t have mod content

Content mods add their biomes and structures at world generation. If you created the world before installing mods (or with different mods), that content won’t be there. You’ll need to generate a new world with your current mod setup.

Lag spikes during boss fights

This is usually CPU, not RAM. tModLoader boss fights can be intense, especially with Calamity’s later bosses. Not much to do except:

• Reduce particle settings where possible
• Accept that some fights are just demanding
• Make sure your server isn’t running on potato hardware (WinterNode doesn’t throttle CPU, which helps here)

Getting started with WinterNode

We run 64-bit tModLoader by default - select it when ordering and you’re ready to go. No extra configuration, no worrying about the 4GB memory ceiling that trips people up elsewhere.

All servers are $1.99/GB. For tModLoader:

• Light mod setups: 3GB ($5.97/month)
• Calamity or Thorium: 4GB ($7.96/month)
• Heavy multi-mod stacks: 6GB ($11.94/month)

Every plan includes automatic backups (handy when mod updates break things), instant setup, and support from people who’ve actually debugged tModLoader issues before.

Got questions? Our support team responds to tickets with actual humans, and we’re active on Discord if you prefer real-time help.