Paper

Massif supports Paper 26.3 and Paper 1.21.11. Your players join with the normal game: only the server needs Massif.

Your server needs Java 25. Paper 1.21.11 itself runs on Java 21, but Massif’s generator needs 25. On a hosting panel, look for a “Java version” or “Docker image” setting.

1. Install the plugin

Download the plugin for your server’s exact version from Downloads and put it in your server’s plugins folder. The 26.3 and 1.21.11 plugins are different files; use the one that matches.

2. Add your world

Download your export from your account and put it at:

plugins/Massif/world.massif

Create the Massif folder if it doesn’t exist yet. The file must be named exactly world.massif.

3. Tell Paper to use Massif

Open bukkit.yml and add (or extend) a worlds section. The world name must match level-name in server.properties, which is world unless you changed it:

worlds:
  world:
    generator: Massif

4. Start on a fresh world

Massif generates new chunks only, so start with a world that hasn’t been generated yet: stop the server, then delete (or move away) the world, world_nether and world_the_end folders, or choose a new level-name.

Start the server and look for Massif’s line in the console. It says which world file it loaded.

If Massif refuses the file, the console says why in one line (for example, the file wasn’t exported by Massif, or it’s for a different Minecraft version). Paper keeps running, but with vanilla terrain: stop the server, fix the file, and delete the world again before anyone explores it, or those vanilla chunks stay in your world.

Updating your world

Export again, replace world.massif and restart the server. Chunks that already exist stay as they are; only new chunks use the new version. For a clean result, start a fresh world again.

Reloading plugins while the server runs isn’t supported: always restart.