How to Set Up a Modded Minecraft Server: Forge, NeoForge, Fabric
To run mods on a Minecraft Java server, install a mod loader (NeoForge, Forge or Fabric) that matches your Minecraft version, then put the mod .jar files in the server's mods folder. Every mod has to be built for that same loader and that same Minecraft version, and players need the same loader, version and, for content mods, the same mods on their side.
This guide covers choosing a loader, the install steps for NeoForge and Fabric, which mods belong on the server, running modpacks and reading a crash. It was checked against the loaders' own documentation in November 2026.
- One loader per server. Mods built for Fabric will not run on NeoForge or Forge, and the reverse.
- Match the mod's Minecraft version exactly. A mod for 1.21.8 may not work on 1.21.11.
- Most Fabric mods also need Fabric API in the
modsfolder. - Remove client-only mods (shaders, minimaps and other visual mods) from the server.
- For a modpack, use its server pack file if it has one. Crashes are explained in
crash-reports/andlogs/latest.log.
On this page
Pick the loader your mods need
You do not choose a loader in the abstract; you choose it because the mods or modpack you want are built for it. Check the mod pages first.
- NeoForge is the loader used by current large packs. For example, All the Mods 10 is a NeoForge pack for Minecraft 1.21.1 on CurseForge. NeoForge's documentation supports multiple versions through the current 26.1 line.
- Forge still publishes builds for current versions; its download page lists builds up to 26.3.
- Fabric describes itself as a modular, lightweight mod loader, and its project says it officially supports Minecraft from 1.14 onward. Most Fabric mods depend on Fabric API.
Check the Java requirement too. Minecraft 26.1 and later needs Java 25 (NeoForge's docs say JDK 25), while Minecraft 1.20.5 through 1.21.11 uses Java 21.
Install a NeoForge server
NeoForge's documentation gives these steps for Linux and Windows. Replace the example version with the one you need.
- Download the installer
Get the installer jar for your NeoForge version from NeoForge's Maven repository, in a new folder for the server.
- Run the installer for a server
Run it with the server option.
java -jar neoforge-installer.jar --installServer - Set your RAM
Open
user_jvm_args.txt, created by the installer, and adjust the memory settings if needed. - Start once, accept the EULA
Start with
run.sh(Linux) orrun.bat(Windows). It stops on the first run. Openeula.txt, changeeula=falsetoeula=true, then start again. - Add mods
A
modsfolder appears after the first start. Stop the server, add your mod files, and start again.
Forge's installer follows the same general pattern for modern versions, but confirm the exact commands on Forge's own download page for your version.
Install a Fabric server
Fabric's simplest route is the server launcher jar. On Fabric's site, choose your Minecraft and loader versions, and download the Executable Server jar. The launcher downloads any missing Fabric Loader and Minecraft files before it starts.
java -Xmx2G -jar <fabric-server-launcher>.jar nogui- Accept the EULA the first time it stops, then start again.
- Place mods in the
modsfolder, along with Fabric API, which most mods require. - The installer's Server tab is the manual alternative; if you upgrade an existing server and see class-loading errors, Fabric's wiki says to delete the old
.fabricfolder.
Which mods go on the server
A dedicated server does not render anything, so mods that only change the client can crash it or do nothing. NeoForge's documentation says client-side mods should be removed from the server, notes that shader and visual-only mods are typical examples, and admits that identifying them often takes trial and error.
- Needed on both sides: mods that add blocks, items, mobs or dimensions. Players must have them too.
- Server-only: some utility or optimisation mods, which players do not need to install. The mod page normally says so.
- Client-only: shaders, minimaps, UI tweaks and similar. Leave them off the server.
Download from sources you trust. NeoForge's docs recommend CurseForge or Modrinth. Always match the loader and Minecraft version shown on the download page, and read the dependencies list.
Running a modpack
Use the pack's server files whenever they exist. The All the Mods 10 page on CurseForge, for instance, ships a separate server pack file. If a pack has none, NeoForge's docs describe installing the normal pack in a launcher, copying its contents into the server folder, and then removing client-side mods.
- Install a server for the same loader and version the pack uses first, then add the pack's files.
- Don't cancel the first run; ATM's guide warns it generates files and that cancelling can force you to start over.
- Check the Java version the pack requires. The wrong Java is one of the most common startup failures.
- Leave
server-ipandserver-portalone unless you have to change them, as ATM's guide advises.
Hosting with ChicagoServers? The Minecraft server hosting page lists what is included, such as one-click mod and modpack installs, free server backups and SFTP file access.
Troubleshooting a crash
When a modded server fails to start or crashes, read these in order:
crash-reports/in the server folder. Fabric's documentation says to start with the summary section and the first mod named in the stack trace, though if several mods appear, the first may not be the real cause.logs/latest.logfor the lines just before the failure, such as a missing dependency or a mod that requires a different loader version.- The mod list in the crash report, to spot duplicates or mods that don't belong.
| Symptom | Likely cause |
|---|---|
| Crash on startup naming a mod | Wrong Minecraft version or loader for that mod, or a missing dependency (often Fabric API) |
| Server won't start at all | Wrong Java version, EULA not accepted, or too little memory |
| Works until a player joins | Missing mod on the client, or a client-only mod on the server |
| Duplicate or version conflict messages | Two copies of the same mod, or mods that require different versions of a library |
If you can't find it, remove half the mods and test, then narrow down. Share a crash report through a paste site when asking an author for help rather than posting it as raw text.
Frequently asked questions
Can I mix Forge, NeoForge and Fabric mods on one server?
No. Each loader needs mods built for it, so a server runs one loader. Use the loader your mods or modpack are built for.
Do players need to install the same mods as the server?
For mods that add content such as blocks, items and dimensions, yes. Some server-only mods don't need installing on the client, and the mod page usually says which.
Why does my modded server crash on startup?
The usual causes are a mod built for a different Minecraft version or loader, a missing dependency such as Fabric API, a client-only mod, the wrong Java version, or too little memory.
Where do I put mods on a Minecraft server?
In the mods folder in the server's main directory. NeoForge creates it after the first start, and Fabric uses the same folder name.