PolarConverter

Free plan

What PolarConverter is

PolarConverter is a free, open-source Java command-line utility for converting Minecraft Java Edition worlds from Anvil format to Polar format for Minestom-based servers. It can process an entire world or limit work to chunks within an optional radius of coordinates (0,0). The source world must contain a region folder and a level.dat file, and Java 25 or later is required. Before conversion, the tool checks whether the world’s DataVersion matches the version supported by Minestom; if not, it stops with an error. During conversion, PolarConverter starts a minimal offline Minestom server to provide block registries and NBT support. It reads Anvil chunks, converts blocks and metadata, and writes a .polar file. The listed dependencies are Minestom, a Minecraft server library, and Polar, which provides Polar world-format support. The project uses the MIT License. It is intended for people working with Anvil worlds for Minestom-based servers. The GitHub releases page states that there are no releases.

Who it suits

PolarConverter suits users preparing Minecraft Java Edition Anvil worlds for Minestom-based servers who can meet its Java and world-file requirements. It may also fit users who want to convert only chunks within a radius of (0,0).

What it does well

Converts complete worlds or a selected chunk radius.
Checks DataVersion compatibility before converting.
Writes converted worlds as .polar files.
Free and licensed under MIT.

What to know first

Requires Java 25 or later.
Input must include a region folder and level.dat.
A DataVersion mismatch stops conversion with an error.
The releases page states there are no releases.

Limits

Conversion requires the world's DataVersion to match the version supported by Minestom; otherwise, it stops with an error.

Getting started

Open the project on GitHub.
Install Java 25 or later.
Prepare a Minecraft Java Edition Anvil world folder containing a region folder and level.dat.
Run the command-line converter on the world, choosing whole-world conversion or a radius around (0,0).
Use the resulting .polar file with a Minestom-based server.

Verdict

PolarConverter has a focused role in moving Anvil worlds into Polar format for Minestom-based servers. Check the Java requirement and DataVersion compatibility before relying on a conversion.

Questions

What does PolarConverter convert?

It converts Minecraft Java Edition worlds in Anvil format into Polar format for Minestom-based servers.

Is PolarConverter free?

Yes. It is free and open source under the MIT License.

What does it require?

It requires Java 25 or later and an Anvil-format Java Edition world folder containing a region folder and level.dat.

Can it convert only part of a world?

Yes. An optional radius limits conversion to chunks around coordinates (0,0).

What happens if the world version is incompatible?

Conversion stops with an error when the world's DataVersion does not match the version supported by Minestom.

Where can I get PolarConverter?

The project is available on GitHub, and its releases page states that there are no releases.

Facts from PolarConverter's own pages

Conversion process: It starts a minimal offline Minestom server for block registries and NBT support, reads Anvil chunks, converts blocks and metadata, and writes a .polar file. · github.com, 4 Oct 2026
Conversion scope: It supports full world conversion or conversion within a specified chunk radius around (0,0). · github.com, 7 Oct 2026
Dependencies: The project lists Minestom and Polar as dependencies for server library and world format support. · github.com, 7 Oct 2026
Downloads: The GitHub releases page states that there are no releases. · github.com, 7 Oct 2026
Full-world conversion: The converter can process an entire world. · github.com, 4 Oct 2026
Input files: The input world folder must contain a region folder and level.dat file. · github.com, 7 Oct 2026
Input requirements: The project requires Java 25+ and a Java Edition Anvil world containing a region folder and level.dat file. · github.com, 4 Oct 2026
Intended users: The project describes compatibility with Minestom based servers, making it relevant to users converting Minecraft worlds for those servers. · github.com, 7 Oct 2026
License: The project states that it is licensed under the MIT License. · github.com, 7 Oct 2026
Maker profile: The GitHub profile describes its developer as focused on creating software, usually for Minecraft. · github.com, 4 Oct 2026
Notable limit: Conversion stops with an error when the world's DataVersion does not match the version supported by Minestom. · github.com, 7 Oct 2026
Operation: The tool starts a minimal offline Minestom server to provide block registries and NBT support during conversion. · github.com, 7 Oct 2026
Output: The converter writes the result as a .polar file. · github.com, 7 Oct 2026
Partial conversion: An optional radius limits conversion to chunks within that radius of coordinates (0,0). · github.com, 4 Oct 2026
Purpose: PolarConverter converts Minecraft Java Edition worlds in Anvil format into Polar world format for Minestom based servers. · github.com, 7 Oct 2026
Requirements: The README lists Java 25 or later and a Minecraft Java Edition world in Anvil format as requirements. · github.com, 7 Oct 2026
Version check: Before converting, it checks that the world's DataVersion matches the Minestom server's supported version. · github.com, 7 Oct 2026
Version requirement: The world’s DataVersion must match the Minestom server’s supported version; otherwise conversion stops with an error. · github.com, 4 Oct 2026

Where PolarConverter stands on Freedom251

Minecraft World Converters#14 of 18