Fix "FML Server with incompatible mods"

What does this error mean?

When trying to connect to a Minecraft server you see in the server list:

• "FML Server with incompatible mods"
• "The server message list is not compatible"

This means your client (your game) and the server don't have the same list of installed mods, or the versions don't match. Forge (FML = Forge Mod Loader) verifies that both sides have exactly the same required mods before allowing the connection.

Main causes

1. Missing mods on your client: The server has mods you don't have installed
2. Different mod versions: You have the same mod but in a different version
3. Extra mods on your client: You have mods the server doesn't recognize
4. Different Forge version: The server uses a different Forge version than yours
5. Different Minecraft version: The server is on 1.20.1 and you're on 1.21, for example

Step 1: Check the server's Minecraft and Forge version

From the panel.baires.host panel, select your server and check in the Startup tab:

• Minecraft version (e.g.: 1.20.1)
• Forge version (e.g.: 47.2.0)

You can also see it in the console when the server starts:

[main/INFO] [FML]: Forge Mod Loader version 47.2.0 for Minecraft 1.20.1

Step 2: Get the exact mod list from the server

From the panel, go to Files → mods/ folder and note all .jar files:

Applied-Energistics-2-forge-15.2.9.jar
JourneyMap-1.20.1-5.9.18-forge.jar
Create-0.5.1.f-forge.jar
JEI-1.20.1-forge-15.3.0.4.jar

Each name includes the exact version — that's what needs to match.

Step 3: Sync mods on your client

Option A: Use the same modpack (recommended)

If the server uses a known modpack (ATM9, RLCraft, Create, Better MC, etc.):

1. Download CurseForge App or Prism Launcher
2. Search for the exact modpack the server uses
3. Install the same version of the modpack (not the latest, the same one)
4. Connect to the server

Option B: Copy mods manually

1. Download and install Forge in the same version as the server from files.minecraftforge.net
2. Download the same mods the server has (ask the admin for the list or download from the panel)
3. Copy them to your mods folder:

• Windows: %appdata%\.minecraft\mods\
• Linux: ~/.minecraft/mods/
• Mac: ~/Library/Application Support/minecraft/mods/

1. Remove any extra mods the server doesn't have (except purely visual mods like OptiFine or Sodium)

Option C: Admin shares a zip

If you're the administrator, you can export mods for your players:

1. From Files in the panel, select the mods/ folder
2. Compress and download it
3. Share the zip with your players so they extract it in their .minecraft/mods/

Step 4: Verify versions are exact

The most common error is having the correct mod but in a different version:

• Server: Create-0.5.1.f-forge.jar → Client: Create-0.5.1.f-forge.jar
• ❌ Server: Create-0.5.1.f-forge.jar → Client: Create-0.5.1.e-forge.jar

One letter difference already causes the error. Each .jar must be identical.

Step 5: Verify client Forge version

1. Open the Minecraft Launcher
2. Go to Installations
3. Verify your Forge profile is the same version as the server
4. If it doesn't match, download the correct installer from files.minecraftforge.net and run it with "Install Client"

Error table and quick fixes

For administrators: diagnosing the problem

See which mod causes the rejection

When a player can't connect, check the server console:

# In the panel console, search for:
rejected
mismatch
missing

This shows exactly which mod or channel is causing the problem.

Share the mod list with players

Create a Discord channel with the exact mod list and versions, or upload a downloadable zip. This prevents 90% of connection issues.

Allow optional client-side mods

Some mods like OptiFine, Sodium or minimaps are client-only. If a player has them and the server doesn't, they normally don't cause issues. But if they cause rejection, the player must remove them.

Summary

1. Verify your Minecraft version matches the server's
2. Install the same Forge version as the server
3. Have exactly the same mods with the same versions
4. Remove extra mods the server doesn't have
5. If using a modpack, make sure you're on the same pack version

If after following all steps you still can't connect, open a ticket on our Discord with a screenshot of the error and we'll help you.