How to Make a Modded Minecraft Server

A modded server runs a mod loader on top of Minecraft. Every mod that adds blocks, items or mobs has to be on both the server and each player's game, at the same version. Get that right and the rest works like any other server.

Everything from a plain server still applies: Java, the EULA, server.properties and letting friends in. If you have not run a server before, start with how to make a Minecraft server, then come back for the mods.

Mods or plugins: which do you need?

• Plugins run on Paper or Spigot and only change the server. Players join with an ordinary, unmodded game. Use them for land claims, ranks, economies and minigames.
• Mods change the game itself and need a mod loader: Fabric, NeoForge or Forge. Mods that add blocks, items, mobs or dimensions must be installed by every player too.

If plugins cover what you want, you do not need a mod loader: switch to Paper instead. Paper cannot load Fabric, NeoForge or Forge mods, and those loaders do not load Paper plugins.

Choose a mod loader: Fabric, NeoForge or Forge

Each mod is built for one loader and one Minecraft version, so the mods you want decide the loader. A modpack tells you which one it uses.

Server-side and client-side mods

Mod pages say where a mod has to be installed. Modrinth lists it as the mod's environment:

• Client and server: mods that add blocks, items, mobs or dimensions. They go on the server and on every player's game.
• Server-side: performance and admin mods. Only the server needs them, so players can join without them.
• Client-side: shaders, minimaps, HUD tweaks and rendering mods such as Sodium. Leave them off the server; some crash it on startup.

How to make a Fabric server

1. Download the server launcher

   On fabricmc.net/use/server, choose your Minecraft version and download Executable Server (.jar). It is a small launcher that downloads the Minecraft server and Fabric Loader on its first run, so there is no installer to run.

2. Run it once

   Put it in an empty folder and start it with the command shown on that page, for example java -Xmx4G -jar fabric-server-mc.26.3-loader.0.19.5-launcher.1.1.2.jar nogui. Like the official server, it stops after creating eula.txt.

3. Accept the EULA and start again

   Set eula=true in eula.txt and run the same command. The world generates. If there is no mods folder yet, create one.

4. Add Fabric API and your mods

   Stop the server, put Fabric API and each mod's .jar into mods, and start it again. Every file must be made for Fabric and for your exact Minecraft version.

How to make a NeoForge or Forge server

1. Download the installer

   Get the installer for your Minecraft version from neoforged.net or files.minecraftforge.net. On Forge's site, choose Installer.

2. Install the server

   In an empty folder, run java -jar followed by the installer's file name and --installServer. Forge's installer also opens a window when double-clicked: choose Install server and pick the folder.

3. Set the memory

   Open user_jvm_args.txt and add a line such as -Xmx6G. Memory and other Java options go in this file, not in run.bat or run.sh.

4. Start it and accept the EULA

   Run run.bat on Windows or ./run.sh on macOS and Linux. It stops on the first run: set eula=true in eula.txt, then run it again.

5. Add your mods

   A mods folder appears after the first start. Stop the server, copy the mod .jar files into it, and start it again.

Run a modpack with its server pack

Players install a modpack with the CurseForge app, the Modrinth App or another launcher. The server needs the matching server files, which many packs publish as a separate server pack.

1. Find the server pack

   On CurseForge, open the modpack's Files tab, pick the version your players use, and look in its additional files for a server pack. On Modrinth, check the pack's description and versions for a server download.

2. Unzip it into an empty folder

   A server pack holds the pack's mods and config folders, and often a start script. Follow any readme inside, accept the EULA, and start it.

3. No server pack? Build one

   Install the pack's loader as a server (above), install the pack in your launcher, and copy its mods, config and other pack folders to the server. Then remove client-side mods such as shaders, minimaps and HUD mods. Finding them can take some trial and error.

4. Keep the versions in step

   Players must use the same pack version as the server. When you update one, update the other.

Many paid hosts can install a modpack from their control panel, which saves most of these steps.

How much RAM a modded server needs

Mods load everything they add when the server starts, before anyone joins, so modded servers need far more memory than vanilla. A light pack with under 50 mods usually runs in 4 to 6 GB; large packs with 200 or more mods often need 8 to 12 GB. Check the pack's own recommendation, then use the server RAM calculator for your player count and view distance.

On Fabric, set memory with -Xmx in the start command; on NeoForge and Forge, in user_jvm_args.txt. If the server lags with memory to spare, the spark profiler mod shows the cause: run /spark profiler, play for a few minutes, then run /spark profiler --stop and open the link it gives you.

Modded server errors and fixes

When nothing points at a culprit, find it by halves: remove half the mods, restart, and keep halving whichever group still breaks. Back up the world before adding, removing or updating mods, because removing a content mod can delete its blocks and items from the world.

Once it runs well, see how other modded servers describe their packs, and add yours to the list so players can find it.