Install the Stoneholm mod on your server

Stoneholm adds underground villages to the world: mazes of halls, stairs, workspaces, abandoned sections and overgrown areas. It works on Fabric or NeoForge, and Modrinth lists it as a server-side mod.

Checked against Stoneholm 2.1.2 on Fabric 1.21.1, October 2026.

What you need

• Fabric or NeoForge on Minecraft 1.21.1. Modrinth lists Stoneholm 2.1.2 builds for 1.20.1, 1.21.1, 1.21.4 and 1.21.10 on Fabric, and for 1.21.1, 1.21.4, 1.21.10, 26.1 and 26.2 on NeoForge. This guide uses 1.21.1, the oldest version that both loaders have a build for, and checked Stoneholm only on that version. The newer builds in the list exist if you want one. Pick the version in JAR Manager and the panel chooses Java for you (Java 21 for 1.21.1).
• Cloth Config API and Fabric API on a Fabric server. The jar asks for both. Modrinth's list for the 1.21.1 file names Cloth Config but not Fabric API, so install Fabric API yourself first. The NeoForge builds need nothing extra.
• Players. Modrinth marks Stoneholm as required on the server and unsupported on the client.

Switch the server to Fabric 1.21.1

1. Open JAR Manager, under More in the left rail.
2. Set Server software to Fabric and Minecraft version to 1.21.1, then press Apply change.
3. Leave Take a backup first ticked, press and hold Confirm & reinstall, and wait for the console to finish.

Your world is kept, but configuration files may be reset. Change your Minecraft version or mod loader covers the switch in full.

Install it

1. Open the Mods tab under Content and leave the Modrinth source chip selected.
2. Search for Fabric API and press Install on it.
3. Search for Stoneholm and press Install. The window lists Cloth Config API as a required add-on, so choose Install all.
4. Go to Console, press Start and accept the EULA prompt the first time.

Find a village

For a clean test of the villages, set World folder in the Config Editor to a new name, press Save changes and restart, which starts a new world. If the Config Editor says server.properties does not exist yet, start the server once first.

The mod has two structures, both defined in its jar. The stone-brick village spawns in forest, hill, jungle, mountain, taiga and savanna biomes, and a deepslate version spawns in mountain biomes. As an operator, run these in game and the game reports coordinates:

• /locate structure stoneholm:underground_village
• /locate structure stoneholm:underground_village_deepslate

Change how big villages are

On Fabric, Stoneholm uses Cloth Config and writes stoneholm.json5 into the config folder after the first start. Open it in the File Manager. It holds one setting, VILLAGE_SIZE, which the file describes as the number of jigsaw generation iterations used to build a village. The default is 25. The mod reads the file once, as it starts, so press Save and restart.

The NeoForge builds ship no config class, so there is nothing to edit there.

Common problems

• The server stops at start and names fabric-api or cloth-config2. Install the missing one from the Mods tab.
• No village anywhere. Run the two /locate commands above to find the nearest one, or test in a new world as described in Find a village.
• Players cannot join. Their game needs to match the server's Minecraft version and loader, and any other mod you add that is required on the client. Use Export for players in the Installed view of the Mods tab for a zip of those, and read Join a modded server from your launcher.
• The server will not start after adding other mods. Fix Minecraft mod and plugin load errors shows how to read the log.