Fix mod and version mismatch errors on a Forge server
Fix Forge errors like missing mandatory dependencies, mod rejections, mismatched mod lists and duplicate mods on your server or when players join.
Updated · 2 min read
Mismatch errors happen when the server, its mods and the players' clients do not all agree on versions. The fix is always the same idea: line up the Minecraft version, the Forge version and every mod version on both sides.
Error on server startup: missing dependencies
Missing or unsupported mandatory dependencies:
Mod ID: 'forge', Requested by: 'examplemod', Expected range: '[47.2,)', Actual version: '47.1.0'
Mod ID: 'curios', Requested by: 'examplemod', Expected range: '[5.4,)', Actual version: '[MISSING]'
Read each line as: mod Requested by needs mod Mod ID within the Expected range, but the server has Actual version.
| Actual version shows | Fix |
|---|---|
[MISSING] | Download and add that dependency mod to mods. |
| A version lower than expected | Update that mod. If the Mod ID is forge, update Forge in your Startup settings. |
| A version higher than allowed | Use an older build of that mod, or a newer build of the mod that requested it. |
Mod ID minecraft | The mod is for a different Minecraft version. Get the right build. |
Version ranges use brackets: [47.2,) means 47.2 or newer, and [1.0,2.0) means at least 1.0 but below 2.0.
Error on server startup: wrong Minecraft version
If a mod built for 1.20.1 is used on 1.19.2, you may see the dependency error above for minecraft, or crashes such as NoSuchMethodError or ClassNotFoundException naming the mod. Every mod jar must be built for the exact Minecraft version the server runs.
Duplicate mods
Found duplicate mods: Mod ID: 'jei' from mod files: jei-1.20.1-15.2.0.jar, jei-1.20.1-15.3.0.jar
Two versions of the same mod are in mods. Delete the older one.
Error when a player joins
Players may see a screen listing mod rejections, missing mods or mismatched mod channel lists, or simply get disconnected with an Incompatible client style message. This means the player's mods differ from the server's.
- Compare the player's
modsfolder with the server's. Content mods must match exactly, including version numbers. - If you run a modpack, make sure both sides use the same pack version.
- Make sure the player uses the same Forge version, or at least one the mods accept.
- Client-only mods on the player's side are usually fine. Missing content mods are not.
A quick way to share the server's mod list is to download the server's mods folder and send it to players, or point them to the exact modpack version.
Vanilla client joining a modded server
A player without Forge, or without the pack, usually gets a message that the server requires mods. They need to install the matching pack or mods.
Avoiding mismatches
- Update the server and the client pack together, never one alone.
- Pin a specific pack version and share it with players when you update.
- Take a snapshot before changing versions, so you can roll back if a mod update breaks the world.