Install Alex's Caves on your server

Alex's Caves is a Forge mod by Alexthe668 and Noonyeyz that adds six rare cave biomes to the Overworld: the Magnetic Caves, the Primordial Caves, the Toxic Caves, the Abyssal Chasm, the Forlorn Hollows and the Candy Cavity. Each has its own blocks, items, mobs and mechanics. It is required on the server and on every player's game.

Checked against Alex's Caves 2.0.2 and Citadel 2.6.3 on Forge 1.20.1, October 2026.

Pick the right server version

The official mod is built for Minecraft 1.20.1 only, and its newest file, 2.0.2, was uploaded on 26 October 2024. The Forge build asks for Forge 47.1.3 or newer. It will not load on Paper, Fabric or a newer Minecraft version.

Open JAR Manager under More, choose Forge under Server software and 1.20.1 under Minecraft version, then press Apply change. The panel picks Java 17 for 1.20.1 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.

Modrinth also lists a separate "Alex's Caves (Unofficial Port)" for NeoForge 1.21.1. Its page says it is community maintained and not affiliated with the original developers, so it is a different project from this guide.

What it needs

Alex's Caves requires Citadel, version 2.6.0 or newer. The newest Citadel for 1.20.1 on Modrinth is 2.6.3.

Install it

1. Open Mods under Content and keep the Modrinth chip selected in the source chip row at the top of the tab. The Game version filter starts on your server's version.
2. Search for Alex's Caves. Add-ons such as "Dimensions of Alex's Caves" appear too, so choose Alex's Caves by AlexModGuy.
3. Press Install. When the "Needs" prompt appears, press Install all so Citadel comes with it.
4. Restart from the Console tab.

The jar is large, about 75 MB. If you upload it by hand instead, the File Manager accepts files up to 100 MB from the browser, and the mods folder is the place for it.

Open the Installed view afterwards. Alex's Caves and Citadel should be listed with no Failed to load badge.

Players need it too

Each player installs Alex's Caves 2.0.2 and Citadel for Forge 1.20.1. 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. The author recommends playing without shaders, because many of them spoil the look of the biomes.

First steps in the game

The biomes are rare, so the mod gives you a starting point. Underground Cabins generate in most Overworld biomes. Inside one is a Spelunkery Table and a barrel of Cave Tablets, with a chance of a Cave Compendium, the in-game guide book to the biomes. The mod's wiki has a Getting Started page.

Cave biomes come with world generation, so they appear in terrain generated after the install. A chunk that already exists doesn't pick up new world generation on its own, so ground you explored earlier keeps what it had.

Settings

After the first start Alex's Caves writes alexscaves-general.toml in the config folder. It includes the average size of a cave biome, the average distance between biomes and how irregular their shapes are. Stop the server before you edit it in the File Manager.

Common problems

• The server stops at startup: open the Console and read the last lines. A missing Citadel is the usual cause. Fix mod and plugin errors on Minecraft covers reading the log.
• The mod is not in the store: the Game version filter follows your server. Only 1.20.1 has a build.
• I can't find a biome: they are exceedingly rare. Start with an Underground Cabin, which has a chance of holding the Cave Compendium.