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If the modpack is already published on CurseForge or Modrinth, using the panel’s Modpack Installer is usually simpler. This guide is intended for custom modpacks that you have assembled yourself.
Before making changes: Stop the server from the Console page and create a backup from Backups. This gives you a way to recover your server if something goes wrong.

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Prepare a Modpack From CurseForge

To gather the files from a CurseForge installation:
  1. Open the CurseForge launcher.
  2. Find the modpack you want to transfer and right-click it.
  3. Select Open Folder.
  4. Create a ZIP archive containing the mods directory.
  5. If your modpack contains any of the following directories, include them in the archive as well:
    • config
    • kubejs
    • defaultconfigs
The resulting archive will contain the files needed to reproduce the modpack on your server.

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Prepare a Modpack From Modrinth

The process is similar when using the Modrinth App:
  1. Open the Modrinth App.
  2. Right-click the modpack you want to install.
  3. Choose Open Folder.
  4. Create a ZIP archive containing the mods folder.
  5. Also include these folders if they exist in the modpack:
    • config
    • kubejs
    • defaultconfigs

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Upload the Modpack to Your Server

Once the archive is ready, upload it to your server.
  1. Open your server in the game panel.
  2. Go to Files.
  3. Upload the ZIP archive.
  4. Once the upload finishes, right-click the archive and select Unarchive.
  5. Confirm that the mods directory and any additional configuration directories are now present.

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Large Modpacks

If the ZIP file is too large to upload through the Files interface, you can transfer it using SFTP. Your SFTP connection information can be found under Settings in the game panel.

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Configure the Minecraft and Mod Loader Versions

Your server needs to use the same Minecraft version and mod loader expected by the modpack. Using an incompatible version can result in startup failures or missing mod errors.

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Forge Servers

If your server is configured to use the Forge server type:
  1. Open the Startup page.
  2. Set Minecraft Version (MC_VERSION) to the version required by your modpack.
  3. Set Forge Version (FORGE_VERSION) to the appropriate Forge version.
  4. Leave Build Type (BUILD_TYPE) set to recommended unless your modpack specifically requires another build.

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Fabric Servers

For a server using Fabric:
  1. Open the Startup page.
  2. Set Minecraft Version (MC_VERSION) to match your modpack.
  3. Set Fabric Loader Version (LOADER_VERSION) to the required loader version.
  4. Set Fabric Version (FABRIC_VERSION) to the version used by the pack.
After configuring the appropriate versions, start the server and monitor the console for errors during startup.

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Troubleshooting Common Problems

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Client-Only Mods

Some mods are designed exclusively for the Minecraft client and should not be installed on the server. Examples can include certain shader-related mods and client-side performance enhancements. Some client-only mods detect this automatically, but others may cause the server to fail during startup. If you identify a client-only mod, remove it from the server’s mods folder.

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Existing World

A custom modpack may require a fresh world, especially if it introduces new terrain generation, biomes, dimensions, or other world-generation changes. For a clean installation, remove the existing world folder from Files before starting the server. If your server uses a different world name, remove the folder specified by the level-name setting in server.properties instead. Create a backup first if you may want to restore the existing world later.

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Different Mod Lists

The mods installed on the client and server generally need to be compatible with one another. If the lists differ, you may encounter connection errors, missing mods, or unexpected behavior. Try reinstalling the modpack on your Minecraft client and then upload the pack to the server again using the steps above. If the issue continues, contact Four Seasons Hosting Support with the server console output and any relevant client logs.

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”Too Many Packets” Error

If you receive a “too many packets” error while attempting to connect, the Packet Fixer mod may help. Install Packet Fixer on both the Minecraft client and server, placing the appropriate JAR file in each mods folder. If the problem remains, temporarily remove mods from both the client and server and test the connection again. Continue narrowing down the mod list until the conflicting mod or combination of mods is identified.