Turning a Client-Only Modpack Into a Working Server Version

Why client and server modpacks are not the same thing

Most packs distributed through third-party launchers like Feed the Beast, ATLauncher, or Technic come in two flavors: a client build for the player and a server build for the host. The client build is what you install on your own machine so you can join a server that is already running the matching server build.

The interesting difference is in the mods themselves. Client builds often ship with mods that have no business living on a server, such as minimaps, shaders, or HUD tweaks. They do not add blocks, mobs, or world logic, so the server gains nothing from running them and will usually crash if you try.

In practice that means almost any client pack can be flipped into a server pack by stripping those purely visual or client-only mods out. The whole challenge is figuring out which mods are safe to keep and which ones have to go.

How to spot a client-only mod

If you have been deep in the modding scene for a while, you can usually eyeball the list and pick out the client extras without thinking. Newer users have a slightly slower path, but it is still very doable:

• Open each mod's project page (CurseForge, the author's site, the modpack wiki) and check whether it says client-only, both sides, or server-only.
• Use this rule of thumb: if the mod adds blocks, mobs, recipes, mechanics, or world generation, it almost certainly belongs on the server. If it only changes how things look or display, it is probably client-side.
• When the documentation is missing, search the mod name plus "server" to see what other hosts have reported.

That is essentially the whole secret. The rest of the work is just file moving.

Step 1: Make sure a server pack does not already exist

Before you spend an evening converting a modpack by hand, confirm that the authors have not already published a server build. The answer depends a lot on the launcher you grabbed the pack from.

• FTB Legacy (Feed the Beast): server builds are almost always provided.
• ATLauncher: server builds are usually provided.
• Technic Platform: sometimes, depending on the pack.
• CurseForge / Curse Launcher: rarely bundles a server build, although individual pack authors often publish one separately.

If a server build is available, download it and skip straight to the upload step at the end. If not, keep going.

Step 2: Locate the client install on disk

To convert the pack, you need access to its installed files. Every launcher exposes the install folder somewhere in its UI, usually right-click the pack or open its settings. Look for an option labeled along the lines of "Open Folder" or "Instance Directory."

Once you are inside that folder, you should see the working directory for that specific pack, including its mods, configs, saves, and so on.

Step 3: Pull out the core modpack files

From the install folder, two directories carry the actual identity of the pack:

• `mods`
• `config`

Everything else, including saves, screenshots, logs and shaders, is local to your machine and not needed on the server. Copy `mods` and `config` into a brand new working folder. That folder is the skeleton of your server pack.

Do not edit anything inside `config` unless you have a specific reason. Mod ID assignments and feature toggles live there, and changing them can cause world corruption or mismatches between client and server.

Step 4: Get the matching Forge server files

Next you need Forge as a server, not as a client. Head to the official Forge downloads page and pick the version that matches what the client pack uses. If you do not remember which Forge version is bundled, launch the client pack once and look at the bottom-left corner of the main menu. The Forge version is printed there.

Once you have the installer, run it and choose the Install server option. Point it at the working folder you just created. The installer will warn you that the folder is not empty. Ignore the warning and continue.

After the installer finishes you should see something like this added to the folder:

• `libraries/`
• `minecraft_server.jar`
• `X.XX.XX-forge.jar`

There is usually also a log file from the installer. You can delete it.

Adding the two folders from the previous step, the working directory should now contain:

• `libraries/`
• `minecraft_server.jar`
• `X.XX.XX-forge.jar`
• `mods/`
• `config/`

That is the full skeleton of a Forge modpack server.

Step 5: Trim the client-only mods

Now walk through the `mods` folder and remove anything that is purely client-side. This is the part that takes time and a bit of judgement. Common offenders:

• Minimap mods (JourneyMap is a notable exception, since it has a server side, but many minimaps do not).
• Shader loaders, optifine-style render tweaks, ambient sound packs.
• Inventory and HUD tweaks that do not register new items.
• Cosmetic capes, dynamic lighting, screenshot helpers.

If you are unsure about a specific mod, keep it for now. A mod that should not be on the server will fail loudly at startup with a clear class or rendering error. A missing server-side mod is harder to debug.

Once you think the folder is clean, do a quick local test. Open a terminal in the folder and run the Forge jar, or set up a small `.bat` (Windows) or `.sh` (Linux) script that calls `java -jar X.XX.XX-forge.jar nogui`. If the server reaches the "Done" line, the conversion worked.

Step 6: Upload to your host and set the startup jar

With a working local build, you can ship it to your hosting account. Upload these to the server root, ideally over FTP or the file manager in your control panel:

• `libraries/`
• `minecraft_server.jar`
• `X.XX.XX-forge.jar`
• `mods/`
• `config/`

Depending on the size of the pack and your upload speed, this can take a while. Hundreds of small mod files transfer slower than a couple of big archives, so be patient.

The last piece is telling your control panel which jar to actually launch. In the server's settings, look for a JAR File field (or Startup Command, depending on the panel) and set it to the full Forge jar filename, for example `X.XX.XX-forge.jar`. Save the change and start the server.

If it boots cleanly and accepts a connection from your client pack, the conversion is done. If it crashes, the console will usually name the offending mod on the first error line, which gives you a clear next move.