World/Worlds

World folder

The world-name folder contains all the information about the world itself, such as chunks (/region/), entities (/entities/), and so on, but also “non-plugin” information about players, such as inventories, locations (/playerdata/), stats (/stats/), or advancements (/advancements/). These files can be found in the folder of main world.

So when someone talks about the world (e.g. delete world), they mean deleting the world folder. The world folder is the world itself.

level.dat

Information about the world itself, such as seed, weather, spawn locations, or game rules, is stored in level.dat file, which is a NBT file.

World types

Main world

The main world of a server is the world that is set at level-name in server.properties. This world stores not only the data of the world itself (its chunks, difficulty, spawn locations, …), but also the “non-plugin” data of the players (inventory, advancements, stats, …). On platforms other than Spigot and its forks, i.e. Vanilla, Fabric, Forge, etc., the nether and end is stored in the DIM1 and DIM-1 folders. On Spigot and its forks, the nether and end worlds have a separate worldName_nether and worldName_the_end folder.

So the main world tends to be the world that has nether and end (these can be turned off if needed, the overworld cannot) and players normally play in it. Using the main world as a spawn-only world, for example, is not suitable, in which case it is more appropriate to use side-world (in the case it’s not the only world).

Every server has a main world. In case it is deleted, a new one is automatically generated when the server starts.

Other world(s) / Side world(s)

Other worlds are worlds that are not main world(s). Only the world itself is stored in these worlds; player data is not stored in them. The Multiverse-Core plugin is most commonly used to manage (create, import, …) such worlds.

Upload World/Import World

Importing the main world

In the case where you want to import a world as main world, just upload the folder (or folders in the case where nether and end have a separate folder) of the world to server root directory and either

1. in server.properties set level-name to the world name (= folder name)

OR

2. rename the world folder(s) to the level-name value from server.properties (i.e. if level-name is set to worldd, rename the world folder to worldd and possibly nether and end to worldd_nether and worldd_the_end)

If you are uploading the world as an archive (i.e. a file in .zip, .tar, .tar.gz, etc.), the file needs to be extracted (unzipped). The world must be a folder, not a file.

Importing other world

In case you want to upload a world as side (other) world, the easiest solution is to use the Multiverse-Core plugin. Upload the world to the server root directory and import it with mv import <worldname> <world type> command (see here)

The world name is the folder name and the world type is NORMAL, NETHER, END, FLAT, LARGEBIOMES or AMPLIFIED.

To teleport to a world, use the mv tp <worldname> command.

If you are uploading the world as an archive (i.e. a file in .zip, .tar, .tar.gz, etc.), you need to extract (unzip) the file. The world must be a folder, not a file.

Deleting a world

Deleting a world is a simple process. Just delete the folder with the world name in the server files (world by default). If the world is large, this process may some time.

Please note - main world contains not only the world itself, but also player data (unless a plugin such as Multiverse-Inventories is used to store this data), such as their inventories, advancements and stats (see here), so deleting the main world will also delete this data.

World generator

The main world generator can be set using generator-settings in server.properties.

Plugin as a generator can be set in bukkit.yml, or in the Multiverse-Core plugin when creating a world using the -g parameter. For example, when creating a world with the VoidGen generator, use the mv create <worldname> <env> -g VoidGen -t FLAT command, or import mv import <worldname> <env> -g VoidGen -t FLAT (see plugin documentation).

Resetting the world

To reset (= delete world and player data while keeping the same seed) the world, just follow the same procedure as for world-deletion, only if the seed is not set in server.properties, before shutting down the server and deleting the world, get the world’s seed with seed and set it in server.properties at level-seed.

Difficulty

The difficulty of the world to be created is determined by the difficulty value in server.properties. Possible difficulty values are peaceful, easy, normal, hard.

If the world already exists, changing the difficulty in server.properties is not enough. The difficulty needs to be changed with the command difficulty <difficulty>. The difficulty is changed in the world in which the command is executed. If the command is executed from the console, the difficulty of main-world is changed.

For versions older than 1.14, the difficulty in server.properties is expressed as a number between 0 and 3 (0 = peaceful, 3 = hard) (these numbers work on new versions, but this may change in the future). For the difficulty command, however, use the difficulty as text and not a number even on old versions.

World name

The name of the main world is determined by the value level-name in server.properties (world in the base).

The world name must not be empty. Otherwise, the server will crash. It should also contain only characters from the English alphabet and numbers, i.e. no diacritics or special characters including spaces. Otherwise the server can work, but you will probably run into problems, especially with some plugins.

Setting the world seed

To change the world seed, you need to shut down the server, delete existing world (if the server has been started at least once, so the world exists), and then set the seed at level-seed in the server.properties file.

When the server is started, the world will be created with the newly set seed. In the case where no seed is set, a randomly generated one is used.

Note: Technically, it is possible to change the seed of a world without deleting already generated chunks. In this case, the already generated chunks will remain, and the newly generated chunks will have the new seed. This is not recommended. Transitions between new and old chunks will be broken. If you would still like to do this for some reason, you can do so by following the instructions below.

1. Set the level-seed in server.properties
2. In the world folder, delete the level.dat and level.dat_old files (the world seed is stored in these files)

Warning! The level.dat file also contains other information (see here), such as the spawn location. If you would like to edit only the seed in level.dat and level.dat_old, instructions on how to edit the contents of such a file can be found here.

Disabling nether and/or end generation

Nether generation can be disabled by setting allow-nether in server.properties to false.

End generation can be disabled by setting the value of allow-end in bukkit.yml to false (only on Spigot and its forks).

Statistics

In the /<main world>/stats/ folder, statistics such as time played, number of deaths, or number of server connections are stored for each player. Since this is a Vanilla feature, stats are collected from the very start of the server. Therefore, the data from these stats is often used to display the time played using placeholders.

World migration

from Spigot to Vanilla/Fabric/Forge

If you want to migrate from Spigot to a platform not based on Spigot (Vanilla, Fabric, Forge, …), you need to manually migrate the worlds. You can read how to do so here: https://docs.papermc.io/paper/migration#to-vanilla

from Vanilla/Fabric/Forge to Spigot

If you want to migrate to Spigot or its fork, the worlds will be converted to Spigot (CraftBukkit) format automatically when you start the server.

Notes

When the generator changes (due to Vanilla generator settings/plugins/version change), already generated chunks will stay the same and newly generated chunks will be generated using the new generator. It is not possible to apply new generator to already generated chunks without deleting the chunks.

Minecraft worlds are saved in the so-called Anvil format. However, for specific cases it is not worth using such a format, as it is inefficient (especially for large minigame servers with many small worlds). That’s why the Slime format was created by the Hypixel team and used for their minigames. You can read more at the following link: https://hypixel.net/threads/dev-blog-5-storing-your-skyblock-island.2190753/

Although there are plugins/platforms that implement and allow you to use this format (e.g. AdvancedSlimePaper or Advanced SlimeWorldManager), they will probably be useless or even counterproductive for you.