Minecraft Modpack Installation

Install a modpack on your Minecraft server using the built-in Modpack Manager, or upload your own pack manually.

Using the Modpack Manager

The Modpack Manager is the easiest way to install modpacks on your server. It pulls data directly from CurseForge and lets you search, browse, and install thousands of modpacks in a few clicks.

Where to Find It

1. Open your server in the Game Panel
2. Click Tools in the navigation menu
3. Select Modpack Manager

You’ll see a searchable list of CurseForge modpacks. Browse or search for the pack you want.

Installing a Modpack

1. Find the modpack you want to install
2. Click the Install button next to it
3. Choose an install option:
   • Install Only: installs the modpack files without touching your existing data
   • Format Server: wipes all server data and installs a clean copy of the modpack

4. Wait for the installation to complete
5. Check that the Server Jar File in your Startup Parameters matches the Forge jar that was installed (e.g. forge-*.jar or server.jar)
6. Start your server

Feed the Beast (FTB) Modpacks

FTB modpacks are no longer updated on CurseForge. The versions in the Modpack Manager may be outdated. For the latest FTB packs, download the server files directly from the FTB website and follow the Manual Modpack Installation guide.

Installing Your Own Modpack

If the modpack you want isn’t on CurseForge, or the Modpack Manager isn’t working for your pack, you can install it manually.

There are two approaches depending on your situation:

CurseForge Pack (Manual)

If the pack is on CurseForge but the automatic installer didn’t work:

1. Download the server files from the pack’s CurseForge page
2. Upload them to your server via SFTP
3. Install the correct version of Forge if it wasn’t included

See Manual Modpack Installation for detailed step-by-step instructions.

Custom Pack

If you’ve built your own modpack or are using a pack from another source:

1. Install the correct version of Forge or Fabric on your server
2. Upload your mods to the mods/ folder via SFTP or the File Manager
3. Upload any required config files to the config/ folder
4. Update the Server Jar File to point to the correct Forge/Fabric jar
5. Start your server

Common Issues

Client-Side Mods Crashing the Server

Some mods only work on the client (your PC) and will crash the server if installed there. This is the most common reason a modded server won’t start after installing a new pack.

What it looks like:

[main/FATAL] [ne.mi.fm.lo.RuntimeDistCleaner/DISTXFORM]: Attempted to load class
net/example/mod/mixin/SomeClientMixin for invalid dist DEDICATED_SERVER

The key phrase is for invalid dist DEDICATED_SERVER. This means the mod tried to load code that only exists on the client.

How to fix it:

1. Check the error for the mod name. It’s usually visible in the class path (e.g. fallingleaves in de/cheaterpaul/fallingleaves/mixin/...)
2. Remove that mod from the server’s mods/ folder
3. Repeat for any other client-only mods

Common client-only mods that will crash a server:

• Shader loaders: Oculus, Iris, OptiFine, Embeddium (rendering)
• Performance/rendering: Dynamic FPS, Better Fps, Entity Culling
• HUD/UI: AppleSkin (client-only version), Jade, WTHIT, Xaero’s Minimap
• Visual effects: Falling Leaves, Particle Rain, Sound Physics

Server Starts as Vanilla Instead of Forge

Your Server Jar File is set to the wrong file. Make sure it’s set to forge-*.jar or server.jar, not minecraft_server.*.jar (that’s the Vanilla jar).

Error: Unable to Access Jarfile

The server can’t find the jar file specified in your Startup Parameters. Either:

• The Forge jar wasn’t included with the modpack. Install Forge yourself.
• The jar has a different name than what’s configured. Update the Server Jar File to match.

Wrong Java Version

If your server crashes on startup with obscure errors, you may be running the wrong Java version for your modpack.

• Minecraft 1.12–1.16 modpacks often require Java 8
• Minecraft 1.17–1.20 modpacks typically need Java 17
• Minecraft 1.21+ modpacks require Java 21

See Java Version Selection to change your server’s Java version.

Can’t Connect After Installing a Modpack

If your server starts but you get Connection Lost or an error when joining:

1. Check your client modpack version. Your client must be running the exact same modpack and version as the server. Open your launcher and confirm the pack version matches
2. Check server.properties and confirm server-port matches your server’s assigned port (found under Management → Allocations)
3. Check the server logs for errors. If the log shows crashes or errors during startup, the modpack may not have installed correctly. See Faulty Install below
4. Restart your server if you’ve changed any values

Faulty Modpack Install

If the modpack didn’t install correctly (missing files, incomplete download, or corrupted extraction), the server may start but crash when players try to join, or fail to start entirely.

Signs of a faulty install:

• Server starts but players get Connection Lost immediately
• Server log shows errors about missing mods or classes
• The mods/ folder has fewer files than expected

How to fix it:

1. Stop your server
2. Delete the mods/ folder and any modpack-generated config files
3. Reinstall the modpack through Tools > Modpack Manager
4. If the Modpack Manager fails again, try the Manual Modpack Installation method instead
5. Start your server and check the logs for a clean startup before connecting

Connection Timeouts on Large Modpacks

Large modpacks can take a long time to sync data to connecting players. If players are getting kicked before they finish loading, the server’s login timeout may be too short.

Mods like RandomPatches (Forge 1.12–1.19) or Packet Fixer (Forge/NeoForge/Fabric 1.15–1.21+) can increase the connection timeout and packet size limits. Install the mod on the server only. Players don’t need it on their client.

Uninstalling a Modpack

What to do depends on whether you want to switch to a different modpack or go back to an unmodded server.

Switch to a different modpack

If you want to replace your current modpack with a different one, archive your server files first so you can switch back later. See Switching Between Modpacks for the full walkthrough.

Go back to Vanilla, Paper, or another unmodded server

1. Take a manual backup if you want to keep your world or configs
2. In the Game Panel, go to Advanced > Server Actions
3. Select the edition you want (e.g. Paper or Vanilla) from the Edition dropdown
4. Enable the FORMAT toggle to remove all modpack files
5. Click Install Different Edition
6. Start your server

For more details on the Edition Installer and available server software, see Using the Edition Installer.