How to Install a Forge Modpack on a Minecraft Server

01Download the server files for your modpack

Almost every popular modpack publishes two downloads: the client pack that launchers install, and a server pack — usually a zip on the pack's CurseForge or Modrinth files page named something like ServerFiles-1.2.3.zip. The server pack is the one you want. It contains the mods and config folders already set up, minus the client-only mods that crash a dedicated server.

Unzip it into an empty folder. If the pack only offers a client download, you can build a server manually — install Forge (step 2), then copy the pack's mods and config folders across — but expect to prune client-only mods in step 5.

02Install the matching Forge version

Many server packs bundle Forge with a start script and you can skip ahead. If yours does not, check the pack page for the exact Minecraft and Forge version it targets (for example, Minecraft 1.20.1 with Forge 47.3.0), download that installer from the official Forge site, and run it inside your server folder:

java -jar forge-1.20.1-47.3.0-installer.jar --installServer

On modern Forge this produces a run.sh / run.bat script and a user_jvm_args.txt file where you set memory, e.g. -Xmx8G. The version must match the pack exactly — Forge builds are not interchangeable between Minecraft versions.

03Check your Java version

The single most common cause of a modded server refusing to boot is the wrong Java. As a rule: Minecraft 1.16.5 and earlier wants Java 8, 1.17.x wants Java 16, and 1.18 onwards wants Java 17 (Java 21 for 1.20.5+). Check what you have with:

java -version

If it is wrong, install the correct runtime (Temurin builds are a safe choice) or point your start script at the right one. On a managed panel, pick the Java version from a dropdown instead.

04Accept the EULA and start the server

Run the start script once. It will generate eula.txt and stop. Open that file, change eula=false to eula=true, and start it again. First boot on a big pack is slow — mod loading plus world generation can take several minutes, so wait for the Done line in the console before judging it crashed.

05Verify the mods folder and remove client-only mods

If the server exits during mod loading, read the crash log — it names the offending mod. Client-only mods are the usual culprits: shader loaders (Iris, Oculus), minimaps, and UI or sound tweaks have no business on a server. Delete the named .jar from the mods folder and start again. Repeat until it boots; a proper server pack should need no pruning at all.

06Connect with the matching client pack

Forge requires the client and server mod lists to line up, so install the same modpack at the same version in your launcher and join via the server's address and port (default 25565). If you later update the pack, update the server and every player's client together — a version mismatch shows up as a red X in the server list or a refusal at login.

Run it on HostPanel: our Minecraft server hosting plans install Forge packs from a one-click list and handle Java versions for you.

Troubleshooting

The server crashes instantly with a long mod-loading error

Nine times out of ten this is a client-only mod (step 5) or a Java mismatch (step 3). The crash report in crash-reports/ names the mod or shows an UnsupportedClassVersionError for wrong Java. Fix the named item and retry — do not delete mods at random.

Players get “Incompatible FML modded server” or a mod list mismatch

The client and server are on different pack versions, or a player is joining with vanilla Minecraft. Everyone must run the same pack version through a modded launcher profile.

The server runs but is unplayably slow or runs out of memory

Big packs need real memory — 6–8GB minimum for 150+ mod packs. Raise -Xmx in user_jvm_args.txt (or your start script), and leave the host OS at least 1–2GB of headroom. If TPS is still poor with adequate RAM, the bottleneck is single-core CPU speed, not memory.