How to make a modded Minecraft server

A modded server runs a mod loader instead of plain Minecraft, and then loads mod files on top of it. On Cobbly you can switch an existing free server to a modded loader, add mods, or install a whole CurseForge modpack in one click — nothing here costs anything. If you do not have a free server yet, make one first.

Pick a mod loader

The loader decides which mods you can run. Most mods target one loader, so check what the mods you want are built for before you choose.

• Fabric — lightweight, updates to new Minecraft versions quickly. Good for performance mods and smaller modpacks.
• Forge — the largest catalogue and what most big, long-running modpacks use. Slower to update to brand-new Minecraft versions.
• NeoForge — a modern fork of Forge; increasingly the default for current-version Forge-style mods.
• Quilt — Fabric-compatible with some extra hooks; runs most Fabric mods.
• Paper / Purpur — not mod loaders. These run plugins, which are server-side only and need no client install. Pick one of these if you want things like economy or claims rather than new blocks and mobs.

Switch your server to a modded loader

Software changes happen while the server is stopped, and they are reversible — you can move back to Vanilla or Paper the same way.

1. On the server page, press Stop if the server is running.
2. Open the Software tab.
3. Choose your loader and the Minecraft version you want.
4. Save, then press Start. The first boot on a new loader takes a little longer while it is downloaded.

Add mods

Once the server is on a modded loader, open the Mods tab to browse and install from CurseForge, or upload jar files yourself in the file manager. The full walkthrough — including what to do when a mod stops the server booting — is in How to add mods to your Minecraft server.

Or install a CurseForge modpack in one click

If you want a ready-made pack rather than hand-picking mods, open the Software tab, choose the CurseForge modpack option, search for the pack and pick a version. Cobbly passes the pack to the server, which downloads and installs the whole server-side pack itself — you do not upload anything. Very large packs can need more memory than the free tier provides; see below.

How much memory a modded server needs

Every free server gets a fixed 3 GB of RAM. That is comfortable for Fabric performance packs and smaller Forge packs, tighter for mid-size packs, and not enough for the heaviest 200-mod packs. How much RAM does a Minecraft server need? breaks down what actually uses it.

Lock it down while you build

A modded server you are still setting up is worth whitelisting so only you and the people you invite can join — and, on a free server, so only they can wake it. See Controlling who can join.