Install Underground Biomes on your server

Underground Biomes adds 24 kinds of stone in metamorphic, igneous and sedimentary styles, each with matching gravel, sand, bricks, slabs, walls, stairs and buttons, plus cobblestone for most of them (the project page lists 16 cobblestone types and no sedimentary cobblestone). Ores and structures such as villages are converted to the local stone when the world generates. CurseForge lists its environment as Client & Server.

Checked against Underground Biomes 1.21-1.4.0 on NeoForge 1.21.1, October 2026.

Pick the right build

The current build is the NeoForge 1.21.1 file undergroundbiomes-1.21-1.4.0.jar, uploaded to CurseForge on 23 August 2026. Its changelog calls it the first NeoForge 1.21.1 release, moved forward from the 1.12.2 line. The jar asks for Minecraft 1.21.1 exactly and NeoForge 21.1.248 or newer.

Older Forge files exist, including Minecraft 1.12.2 (build 1.3.14 is the last) and 1.14.4 (an alpha). Modrinth only carries those two old lines, so for a modern server use CurseForge.

Open JAR Manager under More, choose NeoForge under Server software and 1.21.1 under Minecraft version, then press Apply change. The panel picks Java 21 for 1.21.1 for you. Change your Minecraft version or mod loader has the full steps. Switching reinstalls the server and keeps your world, but make a backup first in the Backups tab.

What it needs

The CurseForge dependency list has no required add-ons. Quark is listed as optional, and the 1.4.0 changelog says the Quark speleothem dependency was removed.

Install it

1. Open Mods under Content. In the source chip row at the top of the tab, pick CurseForge.
2. Search for Underground Biomes. Choose the result by Kreezxil, because other mods have similar names.
3. Press Install.
4. Restart from the Console tab.

Open the Installed view to check. Underground Biomes should be listed with no Failed to load badge.

Players need it too

Each player installs the same build on NeoForge 1.21.1. Join a modded server from your launcher covers the player side, and Fix the mismatched mod channel list error explains the refusal when versions differ.

In the world

The stones are placed during world generation, and the project says ores and structures are converted to the local stone variant then too. The 1.4.0 changelog lists /ubify, for server operators, which forces chunk re-ubification around the player and has a restrata mode to re-apply strata after a config change. It also says chunks are re-ubified automatically when the definitions change. Terrain that has not generated yet is the safe place to look for them.

The 1.4.0 changelog says it updated support for many 1.21.1 ore mods, so ores from other mods blend into the local stone. The project page says a JSON configuration lets you add ores from other mods and disable block variants, and on the 1.21.1 build the first start writes undergroundbiomes-common.toml and an undergroundbiomes folder in the config folder. For the old 1.14 line the page warns about deleting the config/undergroundbiomes folder when you upgrade.

Common problems

• The server stops at startup: open the Console and read the last lines. A wrong Minecraft version or a NeoForge older than 21.1.248 is the usual cause. Fix mod and plugin errors on Minecraft covers reading the log.
• The mod is not in the store: you are on the wrong search source or server version. Use CurseForge, NeoForge and 1.21.1.
• Stone looks vanilla: check that the Installed view lists Underground Biomes with no Failed to load badge, then head for terrain you haven't explored, as covered under In the world.