How to Make a Pixelmon Server

The short version

1. Install a NeoForge 1.21.1 server.
2. Drop the Pixelmon jar into mods/.
3. Start it on Java 21 with enough memory.
4. Give every player the same Pixelmon version.

What Pixelmon is, and which version to run

Pixelmon is a community-made Minecraft mod that brings Pokémon-style creatures, battles and progression into the game. (Pokémon is a trademark of Nintendo; Pixelmon's assets are made by its community.) It runs on Java Edition only — there is no Bedrock version.

The current release, Pixelmon 9.4.1, runs on Minecraft 1.21.1 with NeoForge. Since version 9.3.0 Pixelmon needs NeoForge rather than Forge, and builds for older Minecraft versions no longer receive updates. Pick 9.4.1 unless your group has a reason to stay on an older world.

Prefer something on Fabric, or a different take on the same idea? How to make a Cobblemon server covers the other popular creature mod.

How much RAM a Pixelmon server needs

Pixelmon's own installation guide asks for at least 4 GB of memory for the server, preferably more, depending on players and other mods. In practice:

The official Pixelmon Modpack adds world-generation and quality-of-life mods on top of Pixelmon, which is why it wants more than the mod alone. For how RAM and CPU affect lag, see how much RAM a Minecraft server needs.

Path A: set up a Pixelmon server yourself

1. Install Java 21 on the machine.
2. Install NeoForge. Download the NeoForge installer for 1.21.1 (21.1.248 or the version Pixelmon names), run it and choose Install server into an empty folder.
3. Start once with run.sh or run.bat, accept the EULA by setting eula=true in eula.txt, and stop the server.
4. Add Pixelmon. Put the Pixelmon jar into the mods folder exactly as downloaded — do not unzip it.
5. Set the memory in user_jvm_args.txt, for example -Xmx6G.
6. Start it. If the world was generated before Pixelmon was added, delete it first so spawns and biomes generate correctly. Pixelmon's settings appear in config/pixelmon/ after the first start.

Players connect to your public IP on port 25565, forwarded on your router. The general steps for any modded server are in how to make a modded Minecraft server.

Path B: a hosted Pixelmon server

1. Pick a plan on modded Minecraft hosting: MC Gold for Pixelmon alone, MC Diamond for the modpack.
2. Install it from the Modpacks tab in the panel: search for The Pixelmon Modpack and choose version 9.4.1. Or, for Pixelmon alone, run a NeoForge 1.21.1 server and upload the Pixelmon jar to mods with the file manager.
3. Check Java. In the Startup tab, make sure the server runs on Java 21 before the first start.
4. Start it and share the address. The first start takes a few minutes while the world generates.

Automatic backups are included, so take one before every Pixelmon update. The server stays online without your PC, with a 99.9% Uptime SLA.

How friends join

Every player needs Minecraft Java Edition with the same Pixelmon version as the server — if the versions differ, the game refuses the connection with a "Mod Rejection" error. The easiest way is for everyone to install the same modpack version through a launcher: Pixelmon's site lists the official launcher, ATLauncher, CurseForge, Modrinth and Technic. On the player's side, Pixelmon asks for at least 2 GB of RAM for the game.

Then add the server in Multiplayer with its address and join.

Common Pixelmon server problems

"Mod Rejection" when joining

The player's Pixelmon version is not the server's. Install exactly the same version on both sides.

UnsupportedClassVersionError or the server will not start

The wrong Java version. Pixelmon 9.3.0 and newer needs Java 21 — older and newer Java versions do not work.

Pixelmon does not load on a Forge server

Since 9.3.0 Pixelmon needs NeoForge. A Forge server, or a hybrid server that also runs plugins such as Arclight, will not work with current Pixelmon.

No Pixelmon spawn in an old world

Areas generated before Pixelmon was installed keep their old biomes and spawns. Explore new land, or start a fresh world.