Polar is a world format very similar to Slime, with similar advantages:

• Small file sizes (see SLIME_COMPARISON)
• Single file world
• Immutable (worlds do not save until explicitly requested)
• Store worlds wherever (whether as a file or in a database)
• Great for lobbies and game arenas
• Fast loading and saving

Polar is a world format designed for small to medium sized worlds. File sizes are very small, and worlds save/load quickly. It can be stored as a file or in a database or simply wherever you can store bytes.

Polar is particularly useful for minigames servers where world resets are common and many arenas are used. Changes to the world are only persisted if you tell it to save, and you can create multiple worlds from the same file efficiently so no need to paste arenas far away from each other.

You can also paste worlds like schematics via command or API.

It is similar to Slime (AdvancedSlimePaper), however notably doesn't require a classloader or Paper fork to function. Polar also supports loading and converting from the Slime world format. Currently supports versions 26.3 - 1.21.11

Polar was originally developed for Minestom, see the Minestom library here

Large worlds

Polar is not designed for large worlds!

Polar is most useful when the whole world is mostly within render distance. The entire world is held in memory as a trade-off to allow for faster loading. This means the size/number of worlds you can load depends on how much RAM you have available.

If you need large worlds, it's likely Anvil (the default world format) will be more useful.

Permissions

Permission nodes are simply polarpaper.<subcommand>, for example: polarpaper.info for /polar info

polarpaper.use for the root command (/polar)

Custom gamerules

Polar provides a few custom gamerules that can be defined in the config:

Name	Type	Description
blockPhysics	Boolean	Controls block placement/interaction rules
blockGravity	Boolean	Allow gravity blocks to fall (sand, gravel)
liquidPhysics	Boolean	Allow lava/water to flow
blockFade	Boolean	Controls block fading or disappearing (e.g. snow/ice melting, fire burning out, coral death, turtle eggs)