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PolarConverter

github.com

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Spec score 6.5 #18 of 18 in Minecraft World Converters

What it is

PolarConverter is a free, open-source Java command-line utility that converts Minecraft Java Edition worlds from Anvil format into Polar files for Minestom-based servers. It can process a complete world or limit conversion to chunks within an optional radius around coordinates (0,0). The source folder must contain a region directory and level.dat, and Java 25 or later is required. Before conversion, the tool checks whether the world’s DataVersion matches the version supported by Minestom; a mismatch stops the process with an error. PolarConverter starts a minimal offline Minestom server to provide block registries and NBT support, reads Anvil chunks, converts blocks and metadata, then writes a .polar file. Listed dependencies are Minestom and Polar. The project uses the MIT License and is hosted on GitHub. Its releases page states that no releases are available.

Spec sheet

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

Strong points and limits

Strong points

  • Free and open source
  • Whole-world or radius conversion
  • Writes Polar .polar files
  • Offline conversion process
  • MIT License

Limits

  • Requires Java 25 or later
  • Only Minecraft Java Anvil input
  • DataVersion mismatch stops conversion
  • No GitHub releases listed

Who it suits

It suits developers and server operators preparing Minecraft Java Edition Anvil worlds for Minestom servers. Users need Java 25 or later and correctly structured world files.

Verdict

PolarConverter offers a focused Anvil-to-Polar workflow for Minestom projects, including optional radius selection and offline processing. Verify Java, folder contents and DataVersion compatibility before running it.

Where Specifiction places it

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