Choose the loader first
Fabric, Forge and NeoForge are different ecosystems. A mod built for one loader is not automatically compatible with another, even if the Minecraft version number is the same.
Match Minecraft, loader and mod versions
The server and players need a compatible combination of Minecraft version, loader version and mod versions. Modpack authors often provide a tested combination; reproducing that exact set is safer than mixing arbitrary releases.
Install server-side files
- 1Stop the server.
- 2Back up the world and configuration.
- 3Install or update the required loader using its documented server process.
- 4Place compatible mod jars in the server's mods directory.
- 5Start the server and inspect the console for dependency or version errors.
- 6Only then update the player clients to the matching set.
Client-only and server-only mods
Not every mod belongs on both sides. Some are client-only visual/UI mods, while others are server-side utilities. Follow the mod author's installation requirements instead of copying an entire client mods folder blindly to the server.