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Adding Additional Mods to your Minecraft Modded Server

When playing a modded Minecraft server you may want to add mods to it to alter the experience or include something that you feel the pack is missing. Below you will find all the steps required to add the additional mods to your server as well as methods for using FTP access to update and restart everything.


  1. Installing Minecraft Mods on your Server
    1. First Checks
    2. Adding the Mod To Your Server
    3. Optional Steps
  2. Adding Additional Mods to Modpacks in Singleplayer
  3. Troubleshooting
    1. IndexoutofBoundsException
    2. MissingModsException
  4. Further Reading & External Links

Installing Minecraft mods on your server

First Checks

  • Make sure your server and local pack are running the same Minecraft version.
  • Make sure that the pack is running without problems before you add the mods.
  • Ensure that the pack version matches in your launcher and on the server.
  • In case anything goes wrong, take a backup of your Minecraft world. For information on how to do this, you can follow our guide: How To: Backup Your Minecraft World

Adding the Mod To Your Server

  1. Stop your server.
  2. Connect to your server using the Multicraft FTP or your chosen FTP software.
    There are multiple methods for connecting with FTP. Read this for more information on using Multicraft:
    How to: Use FTP to Upload and Download Files
  3. Upload the mod you are adding to the mods folder.
    If this folder doesn't exist, make sure you have started your modded server at least before, the server should make the folder when you start it the first time. So if you do not see the folder, start then stop your server.
  4. Start the server.

Optional Steps

  1. If you wish to make adjustments to the mods configuration then stop your server again.
  2. Using your FTP connection of choice, open the configs folder and navigate to the configuration file that is relevant to the mod you just added.
  3. Config files can also be edited directly through the control panel: How To: Edit Mod Configuration Files
  4. If there is a crash or problems loading check our Troubleshooting section below.



Newly added mods will not have configuration files. You will need to run a server restart at least once to generate all the files for configuring the mod and making adjustments.

Adding Additional Mods to Modpacks in Singleplayer

If you are interested in adding mods to your singleplayer modded Minecraft, you can follow our instructions here:
How to: Add Minecraft Forge Mods to a Singleplayer Game


When adding mods to existing modpacks there is a chance that something will go wrong, these are some of the most common issues that occur. Most importantly, following the First checks section above can prevent a lot of these problems.
Keep in mind that some mod authors will have customised and adjusted their pack to work exclusively or in a more integrated way with the mods that it comes with when installed and support for additional mods may not exist.


    at java.nio.Buffer.checkIndex(

This error may relate to an issue with the configuration files of the new mods. The quickest way to test this as the cause is to delete the configuration files of the mods that were added and then run the modpack again to allow new configurations to generate.
If this doesn’t work, the error is being caused by something else.

Firstly check the issue tracker, bug reports and comments sections for the mod to see if it is a common error or unique to you.
If you do not find a solution, open a support ticket with the mod author giving details of the error.


    at cpw.mods.fml.common.Loader.sortModList(

This error is an indication that either the mods list on your local computer and the server aren't the same as each other or that the mods in them have different versions.
Usually, this error will be accompanied by a mod and version number. Make a note of this before checking your local files and your server files for that mod to make sure they match.

Occassionally a crash may be a little more in-depth and related to a specific mod being broken or some other more technical issue.
We always recommend checking the mod's support, issues, and comments pages to see if anyone else has suffered the error and potentially found a solution. As well as sending a message or opening a Ticket with the Mod author if a fix is not clear.

Further Reading and External Links

StickyPiston Support

If you use our services or not, we are always happy to help. Open a support ticket and our dedicated team will be in touch.

Open Support Ticket

  • Installation, Modded
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