Mod Observer

Mod that checks other mod's presence. Upon joining a server that requires you to install this mod, it checks, if the loaded mods are allowed or not.

7.8K Downloads

fabricmanagementsocial

Rent Server with this Mod

Screenshots

About this Mod

DISCLAIMER: This project is experimental

ModObserver, as the name suggests, observes, which mods are loaded, and upon joining a server, sends those mods to the server. The server owner can adjust, which mods are allowed and which are not.

When you try to join a server, that requires you to have ModObserver, you will get a kick message similar to this one:
ModObserver required message

For server owners: if you want ModObserver on your server, download this plugin: https://modrinth.com/plugin/mod-observer-plugin

Available Versions

Mod Observer 3.0.2release

MC 1.21.11fabric

December 22, 2025

Mod Observer 3.0.2release

MC 1.21.9, 1.21.10fabric

November 29, 2025

Mod Observer 3.0.2release

MC 1.21.7, 1.21.8fabric

November 29, 2025

Mod Observer 3.0.1release

MC 1.21.9, 1.21.10fabric

November 27, 2025

Mod Observer 2.1.3release

MC 1.21.9, 1.21.10, 1.21.11fabric

October 7, 2025

How to Install Mod Observer on Your Server

Order Server

Order a Minecraft Java server with at least 3 GB RAM (4 GB recommended).

Set fabric Loader

In the panel under "Egg", select the fabric loader and matching Minecraft version (1.21.11).

Install Mod

Open the mod browser in the dashboard and search for "Mod Observer". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.

Compatibility

Mod Loaders

fabric

Minecraft Versions

1.21.11, 1.21.10, 1.21.9 (+14 more)

Server-side

~ Optional

Recommended RAM

4 GB(min. 3 GB)

Frequently Asked Questions

Mod Observer server crashes on startup – what to do?

Most common cause: wrong fabric version or insufficient RAM. Check the server log (latest.log) for "OutOfMemoryError" or "Mixin" errors. With Mado Hosting: ensure at least 3 GB RAM is allocated and the loader matches the mod version (1.21.11). You can switch loaders with one click in the panel.

Is Mod Observer compatible with fabric?

Mod Observer officially supports fabric for Minecraft 1.21.11, 1.21.10, 1.21.9. The Mado dashboard automatically detects incompatible loader combinations.

Server lagging with Mod Observer – how to optimize performance?

Recommended RAM: 4 GB (per 8 players). Use /spark profiler to check if Mod Observer consumes the most tick time. Common fixes: reduce server view-distance to 8-10, install "performant" or "starlight" as supplementary mods on Forge. With Mado Hosting, your server runs on NVMe SSDs with dedicated CPU cores for minimal latency.