---
title: "How to Make a Pixelmon Server: NeoForge Setup, Rules and Errors"
description: "Set up a Pixelmon 9.3.16 server on Minecraft 1.21.1 and NeoForge: the server jar, Java 21, config, Pixelmon's server rules and the Mod Rejection error."
url: "https://www.gameserverkings.com/knowledge-base/minecraft/pixelmon-server/"
category: "Minecraft"
category_url: "https://www.gameserverkings.com/knowledge-base/minecraft/"
published: "2026-09-28T03:14:09.224Z"
updated: "2026-09-28T03:14:09.224Z"
source_format: "markdown"
site: "GameServerKings"
---

# How to Make a Pixelmon Server: NeoForge Setup, Rules and Errors

A Pixelmon server is a NeoForge server with one mod in it. Pixelmon isn't a modpack, so you don't need a server pack or a launcher export. You need the right Minecraft version, the right loader, Java 21 and one jar downloaded from the Pixelmon team's own site. Most failed Pixelmon servers get one of those four wrong, or run a copy of the mod that came from somewhere else.

This guide covers the current Pixelmon release, how to set it up on a GameServerKings server, what Pixelmon's own terms say you must and must not do on a server, and the errors players hit when they try to join.

> [!IMPORTANT] Pixelmon today: 9.3.16 on Minecraft 1.21.1, NeoForge only
> As of September 2026 the recommended build is **Pixelmon 9.3.16** for **Minecraft 1.21.1**, and **9.4.1** is the current beta. The [official site](https://reforged.gg/) lists NeoForge 21.1.200 for 9.3.16 and says 9.4.1 needs *"at least"* NeoForge 21.1.248. Since 9.3.0, Pixelmon runs on NeoForge, not Forge. Old guides that tell you to install Forge are for 1.16.5 and 1.20.x Pixelmon.

## What a Pixelmon Server Needs

| | Requirement | Where it comes from |
|---|---|---|
| Minecraft | 1.21.1 exactly | The jar declares `minecraft [1.21.1,1.21.2)` |
| Loader | NeoForge 21.1.x | The jar requires `neoforge [21.1.0,)`. The 9.4.x beta needs 21.1.248 or newer |
| Java | 21 | [Pixelmon wiki](https://pixelmonmod.com/wiki/Server_installation): *"Java 21 for 9.3.0 or above"* |
| Memory | 4 GB minimum | Same page: *"At least 4 GB of allocated memory, preferably more. Exact requirements will depend on player count and your exact mods/plugins."* |
| The mod | The **-server** jar from reforged.gg | The wiki: the -server file *"is much smaller … but will only work on servers"* |

Older versions still exist (9.2.x for 1.20.1 and 1.20.2, 9.1.12 for 1.16.5), but the wiki notes that Pixelmon for older Minecraft versions *"will no longer receive updates or bug fixes"*. Start a new server on 1.21.1.

## Setting Up Pixelmon on GameServerKings

Take a backup from the **Backups** tab first if the server already has a world you care about ([How to create a backup](/knowledge-base/general/how-to-create-a-backup/)).

1. **Startup tab.** Set **Framework** to `NEOFORGE` and **Minecraft Version** to `1.21.1`. Set the **Docker Image** to `Java 21`.

2. **Settings tab → Reinstall.** The install script downloads NeoForge for you. It picks the newest non-beta NeoForge build for 1.21.1 (21.1.252 in late September 2026), which is newer than both minimums above. The **Build Number** variable has no effect on NeoForge, so leave it alone. Reinstalling keeps your `world/`, `mods/`, `config/` and `server.properties`.

3. **Download the server jar** from [reforged.gg](https://reforged.gg/). It is the *Server Jar 1.21.1* link under the NeoForge link for the version you want (for 9.3.16 the file is `Pixelmon-1.21.1-9.3.16-server.jar`, about 41 MB).

4. **Upload it into `mods/`** from the **Files** tab. At 41 MB it fits the browser uploader. SFTP on port 2022 works too ([How to upload files via SFTP](/knowledge-base/general/how-to-upload-files-via-sftp/)). Don't unzip or rename it. The wiki says: *"Do not extract or otherwise change this file!"*

5. **Decide about the old world.** If this server already generated a world before Pixelmon was added, the wiki recommends deleting it so that *"players will initially spawn in a Village as intended and Pixelmon features … will generate near spawn."* Stop the server and delete the `world` folder (or whatever `level-name` says in `server.properties`) if it is disposable.

6. **Start the server** and watch the **Console**.

> [!WARNING] Coming from Paper? Watch for "Missing data pack paper"
> New GameServerKings servers start on Paper. If you keep a world that Paper created, the first NeoForge start can fail with *Missing data pack paper*. The fix, which the install log also prints: set **Extra Flags** to `--safeMode`, start once, stop, then clear **Extra Flags**.

Your heap is set by the plan, not by a file: the server starts with `-XX:MaxRAMPercentage=95.0`, so it gets 95% of the plan's RAM. Pixelmon's `user_jvm_args.txt` advice is for home servers and does nothing here. If 4 GB is tight once players arrive, that's a plan change. [Minecraft Server RAM and JVM Flags](/knowledge-base/minecraft/allocating-ram-and-jvm-flags/) explains the sizing.

## Configuring Pixelmon

After the first successful boot, Pixelmon writes its settings under `config/pixelmon/`, split into several files. The wiki's [Configs](https://pixelmonmod.com/wiki/Configs) page describes every key. Two things to do early:

- **Change PokeLoot's `spawnMode` before players explore.** The wiki is direct: *"To avoid loot drain over time, be sure to change spawnMode under PokeLoot now!"*
- **Set world-generation options before the world is explored.** The wiki warns that *"some settings will only apply to fresh chunks"*.

Edit them with the server stopped, then start it again.

### Sidemods and permissions

Sidemods are extra jars built on Pixelmon (shops, battle tools and so on). They go in `mods/` next to Pixelmon and need a restart. Check each sidemod's page for the Pixelmon version it targets and its own requirements. The wiki notes some need *"additional libraries … or a permissions manager such as LuckPerms"*. LuckPerms publishes a NeoForge build, and [How to Set Up LuckPerms Permissions](/knowledge-base/minecraft/luckperms-permissions/) covers the commands.

> [!CAUTION] No Bukkit plugins on current Pixelmon
> The Paper plugins from other guides won't load on a NeoForge server. The old workaround, the Arclight hybrid server, is ruled out by the Pixelmon wiki itself: *"Arclight is not compatible with Pixelmon 9.2.4+"*.

## Pixelmon's Server Rules

Pixelmon's own [Terms of use](https://pixelmonmod.com/ucp.php?mode=terms) include a section for servers. In short:

- **State your independence.** *"When using Pixelmon on a server, you must state that the server is not affiliated with Mojang AB … and you must also note that you hold no affiliation with the Pixelmon Mod development team, website or overhead company."* Put it in your Discord, website or server rules, wherever players will see it.
- **Don't redistribute the jar.** *"Distribution of this mod is only permitted to the Pixelmon Mod website, via our downloads page. Redistribution in any form, whether it be public or private modpack, alternate download link, direct download link to the software … is strictly prohibited."* Tell players to install Pixelmon from reforged.gg or through a launcher that installs it from there (the site links CurseForge, Modrinth, ATLauncher and Technic). Don't upload the jar to your own Discord or site.
- **Don't modify it.** *"Do not alter any compiled version of The Mod in any way."*
- **Leave cosmetics alone.** *"Please do not sell, alter, block use of to players, or falsify the player cosmetics."* Those are donor perks from the Pixelmon team, not yours to sell.
- **You also have to follow Minecraft's EULA.** The same terms: *"To use The Mod on a server, you must agree to the Mojang EULA"*. What Mojang allows you to sell is in [Minecraft Server Monetisation: What Mojang Actually Allows](/knowledge-base/minecraft/monetising-your-server/). We found no separate Pixelmon rule on selling ranks or other items beyond the cosmetics line.

If you list your server on Pixelmon's forum, its listing rules add: no *"hacked versions of Pixelmon"* or *"cracked Minecraft"*, and don't give your server *"a generic name like 'new server' or 'Pixelmon server'"*. And there is no official Pixelmon server to compete with. The FAQ says *"There are no official servers, and anybody claiming otherwise is lying to you."*

## Getting Players Connected

Every player needs the same Pixelmon version as the server, on Minecraft 1.21.1 with NeoForge. The easy route is a launcher: *The Pixelmon Modpack* on CurseForge or Modrinth installs the mod and NeoForge in one go. Tell players which Pixelmon version you run, and whether it is the recommended build or the beta, because launchers may offer the newer one.

Pixelmon's client jar (*universal*) and server jar are different files built from the same version. That's expected. Players install the full client build, and the server runs the -server one.

## Common Pixelmon Server Errors

| What you see | Cause | Fix |
|---|---|---|
| Player gets a **"Mod Rejection"** error | Different Pixelmon versions. The wiki: *"If their version differs, they will be shown a "Mod Rejection" error and will be unable to join."* | Match the player's Pixelmon version to the server's exactly |
| Server exits at once with a Java version or class-version error | Wrong Docker image | Set **Docker Image** to `Java 21` and restart. No reinstall needed |
| Server ignores Pixelmon and boots like vanilla or Paper | **Framework** is still `PAPER`, or the jar isn't in `mods/` | Set `NEOFORGE`, reinstall, check the jar sits directly in `mods/` |
| `Missing data pack paper` on first start | World created under Paper | Run once with **Extra Flags** `--safeMode`, then clear it |
| Players connect, then lag or the server logs `Can't keep up!` | Too little RAM, or too many players for the plan | See [Can't keep up!](/knowledge-base/minecraft/error-cant-keep-up/) and [Diagnosing Lag](/knowledge-base/minecraft/diagnosing-lag-and-low-tps/) |
| Server crashes with `java.lang.OutOfMemoryError` | Heap too small for the players and sidemods | See [OutOfMemoryError: Java heap space](/knowledge-base/minecraft/error-out-of-memory-java-heap/). The fix is a bigger plan, not a flag |

For anything else, the crash report names the failing mod. [Reading Minecraft Server Logs and Crash Reports](/knowledge-base/minecraft/reading-crash-logs-and-common-errors/) shows where to look. The general modpack workflow (backups before updates, keeping players in sync) is in [How to Make a Modded Minecraft Server](/knowledge-base/minecraft/installing-modpacks/).

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