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How to Upload a Custom JAR File For Minecraft

Last modified on Mar 24, 2023 in Control Panel

mc head By Nathan Young


Creating a Minecraft server may involve plugins or mods, which needs a specific configuration to fully work. This tends to be Paper or Forge JARs, which is built into our panel system. However, sometimes owners want or need a specific version of them for a variety of reasons. For instance, occasionally mods require a certain Forge build and not the latest one. Other times, it can be a completely customized setup of their liking. Regardless of your reasoning, doing this can be confusing for newcomers or anyone inexperienced with servers. With this in mind, we’ve created this Apex Hosting tutorial to show you how to upload a custom JAR into a Minecraft server.

Custom JARs

Briefly mentioned above, custom JARs are used for specific versions of server types. There are tons of possibilities other than Paper or Forge, such as Magma, Fabric, and more. Obtaining these involves you downloading them from their respective websites, which could contain other files. For example, modded JARs typically have a “libraries” folder that holds important data. These are, most of the time, essential for the server to successfully load up. The process for installing it has a few steps, which can be reviewed down below.


Before uploading anything, you’ll need to prepare the server and files first.

  1. Head towards your Apex server panel, then locate the Game File area.
  2. Click on the currently used option, then search for Custom Server Jar.
    Minecraft Custom Server JAR

    Note: Make sure to use the correct Server Profile for this setup.

  3. Once found, select it and press Change Version in the following prompt.
    Loading Minecraft Custom JAR
  4. Afterward, click the Create New World and I’ll Restart Later buttons.
  5. When you’re done, confirm custom.jar is used for the filename.
    Minecraft Custom Server

    Important: If you see a different name, change it accordingly.

  6. On your computer, locate your desired JAR file and rename it to custom.jar.
    Minecraft Custom JAR File


We strongly encourage you to create a new world, as it fully ensures compatibility with the new JAR file. However, if the existing map shares the same Minecraft version and/or mods, then it should be supported. Otherwise, continue to make a fresh world to proceed with the installation.


Uploading to Server

When everything is prepared, follow the instructions below to install the custom JAR file.

  1. In the main server panel, click FTP File Access near the top left corner.
    Minecraft FTP Server
  2. Login with your password, then locate and enter the jar directory.
    Minecraft Server JAR Folder
  3. Checkmark any existing files, then press Delete at the top.
    Minecraft Delete Server Files
  4. Submit these changes, then wait for it to complete and return to the same folder.
  5. Afterward, press Upload in the top left corner to begin the installation process.
    Minecraft Server Upload Button
  6. Drag and drop the custom.jar file into the respective area.
    Minecraft Uploading Custom JAR File
  7. Wait for this to reach 100%, then head back to the main panel.
  8. Restart the server so the new JAR can load without problems.


Extra Files

In most cases, owners will have extra files that were downloaded with their custom JAR. These can also be uploaded to the server, which may be required depending on what you’re using. The steps to upload the other files are the same as above, but requires them to be zipped via WinRAR or 7zip. Once they’ve been compressed, you’re ready to follow the steps below.

  1. Navigate to the FTP File Access page from the main server panel.
  2. Login, then enter the jar directory and press Upload in the top left.
  3. Drag and drop the zip into the respective area, then wait for it to complete.
    Minecraft Uploading Server Files
  4. Return to the main folder and check mark the uploaded zipped file.
  5. Press Unzip in the top right corner, then Submit the changes on the next page.
    Minecraft Unzip Server Files
  6. Wait for everything to finish, then head back to the main panel.
  7. From here, Restart the server so the custom JAR can successfully load.


Common Issues

Custom JAR Isn’t Loading

In cases when the JAR isn’t loading after uploading it, ensure that you’ve set the file name to “custom.jar”. This is absolutely necessary for everything to work properly. Additionally, the Game File area needs to have the same name selected for it to start. If the situation persists after this, then double-check you didn’t miss any Extra Files during the FTP uploading process. Once everything is done, Restart the server to see if it loads correctly. However, there could be an underlying issue with the JAR file itself that causes the problem.

Unable to Join Server

Sometimes, players may be unable to join the server due to another issue other than the custom JAR. This happens if you didn’t create a new world, which tends to be required for most installations due to incompatibility concerns. Although, another cause could be from missing mods on your launcher or using the wrong game version to join the server. Confirming these aspects, depending on your setup, will likely resolve the issue. Otherwise, try to use the Direct Connection method with your IP Address:Port for the best possible attempt.

Useful Links

Connecting via FTP to Minecraft Servers
How to Create a New World in Minecraft
Setup and Play on Paper Servers
How to Use Server Profiles

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