Below is a simple and reliable guide for uploading your own world (singleplayer save, custom map, or backup) to a Minecraft Java server (Spigot, Paper, or Vanilla).
If you follow the steps correctly, it always works.

1. Prepare Your World

1. Open your Minecraft saves folder:

   Windows:
   %appdata%/.minecraft/saves/

   Mac:
   ~/Library/Application Support/minecraft/saves/

   Linux:
   ~/.minecraft/saves/

2. Find the folder of the world you want to upload.
   It must contain files like:
   level.dat, region/, data/, playerdata/, etc.

3. Rename the folder to:

   • world (if you want to replace the default server world),
     or
   • world2, creativeworld, etc. (if you want to add it as an extra world using Multiverse).

2. Access Your Server Files

You can connect in two ways:

1. File Manager (Pterodactyl, Multicraft, etc.) Open the File Manager and go to the server’s main directory.

2. FTP (FileZilla) Log in using your FTP credentials and open the server’s main directory.

3. Stop the Server

This is crucial - never upload or replace a world while the server is running.
Click Stop and wait until it fully shuts down.

4. Remove the Old World (If You Want to Replace It)

If you're replacing the main world, delete these folders:

world
world_nether
world_the_end

(Or delete only the worlds you want to replace.)

5. Upload Your World Folder

1. Upload the world folder (world, world2, etc.) to the root directory of your server.
2. Make sure the folder contains level.dat — without it, the world won’t load.

If your panel requires a ZIP file:

• Zip your world folder → upload → click “Extract”.

6. Update server.properties (Only When Replacing the Main World)

If your world folder has a custom name, tell the server to load it.

Open: server.properties Find the line: level-name=world Change world to your world folder’s name. Example: level-name=customworld

7. Start the Server

Click Start.

If everything is correct:

• the server will load your uploaded world,
• players will spawn inside your imported map,
• nothing will be overwritten.

8. Uploading a World as a Second World (Multiverse)

If you want to keep the original world and add another one:

1. Upload your world folder (e.g., world2) to the server.
2. Start the server.
3. Import the world using:

Normal world:

/mv import world2 normal

Nether:

/mv import world2 nether

End:

/mv import world2 end

Teleportation:

/mv tp world2

9. Common Problems (and How to Fix Them)

Uploaded a ZIP instead of a folder - missing level.dat

• Extract the ZIP and upload the full folder.

Server loads a new empty world

• Wrong world name in level-name.
• The uploaded folder does not contain level.dat.

World fails to import in Multiverse

• Use the correct type (normal, nether, end).

Server crashes after uploading the world

• Files are corrupted or incomplete - re-upload the entire folder.