Region Converter

Rust command-line tool for converting Minecraft Java Edition region saves between:

• mca (.mca)

  Minecraft's default save format, supported by all servers.

• linear (.linear)

  A compressed format, supported by LinearPurpur, Kaiiju, LeavesMC and Luminol.

• blinear_v2 (.b_linear)

  The next-generation compression format, a reimplemented linear, created by Luminol.

• blinear_v3 (.b_linear)

  The third generation of blinear, supported by Luminol, provides better performance and stability.

Features

• Parallel conversion with a configurable worker count
• Automatic use of available CPU threads when --threads is not set, capped to the discovered region-file count to avoid idle workers
• Compression level control for compressed target formats
• Works on Windows and Linux
• Reads classic linear v1/v2 files and modern linear v3 files
• Writes linear output in the modern linear v3 layout
• Skips corrupted chunks when the format allows chunk-level recovery
• Fails corrupted whole-region inputs without producing partial garbage
• Accepts one or more world directories, region directories, or single region files
• Supports --info mode for detailed save statistics without conversion
• Prints a concise conversion summary before work starts
• Shows live progress in a single line with completed regions, successful chunks, discarded chunks, warning counts, and chunk throughput
• Writes each completed region file to the output path immediately instead of waiting for the whole batch to finish

Build

cargo build --release

Usage

cargo run --release -- \
  --to blinear-v3 \
  --output /path/to/output \
  /path/to/world

Common options

--from <auto|mca|linear|blinear-v2|blinear-v3>
--to <mca|linear|blinear-v2|blinear-v3>
--output <PATH>
--info
--threads <N>
--compression-level <LEVEL>

Examples

Convert a world directory to blinear_v3:

cargo run --release -- \
  --to blinear-v3 \
  --output /data/out \
  /data/world

Convert multiple region directories at once:

cargo run --release -- \
  --to mca \
  --threads 16 \
  --compression-level 6 \
  --output /data/out \
  /data/world/region \
  /data/world_nether/region

Convert with a fixed source format instead of auto-detection:

cargo run --release -- \
  --from blinear-v2 \
  --to linear \
  --output /data/out \
  /data/world

Convert a single region file:

cargo run --release -- \
  --to mca \
  --output /data/out \
  /data/world/region/r.0.0.linear

Inspect a save without converting:

cargo run --release -- --info /data/world

Inspect a single region file:

cargo run --release -- --info /data/world/region/r.0.0.b_linear

Runtime output

Before conversion starts, the CLI prints:

• input paths
• output path
• source-format mode and target format
• effective worker-thread count
• compression level
• total region-file count

During conversion, the CLI shows live progress including:

• completed region files versus total region files
• successful chunk count and discarded chunk count
• warnings seen so far
• chunks per second

With --info, the CLI prints:

• input type for each path (world directory, region directory, or region file)
• total storage size
• detected storage-format breakdown
• region-file count and readable/failed region counts
• decoded chunk count, discarded chunks, and warnings
• per-file details when the input itself is a single region file

Compression levels

• mca: zlib 0..=9
• linear, blinear_v2, blinear_v3: zstd 1..=22

Default compression level is 6.

Input discovery

If an input path is a supported region file, it is treated as a single-file input.

If an input directory directly contains region files, it is treated as a region directory.

If it does not, the converter searches recursively and treats the input as a world directory. Any nested directory that directly contains supported region files is converted, which covers layouts such as:

• world/region
• world/DIM-1/region
• world/DIM1/region

Output layout

• directory inputs are written under --output/<input-folder-name>__<hash>/...
• world inputs keep their internal relative region-directory structure inside that folder
• region-directory inputs write their region files directly inside that folder
• single region-file inputs are written directly under --output
• the hash suffix is stable for each source path, which keeps same-named directories from colliding across different runs

Corruption handling

• Broken chunks are skipped with warnings when the format has enough structure to recover the rest of the region.
• Broken whole-region payloads fail that region file and leave other region files running.
• The process exits with a non-zero status if warnings or errors were encountered.

Notes

• linear input compatibility covers classic linear v1/v2 and the newer linear v3 layout from the referenced server implementation.
• linear output is written as linear v3.
• blinear_v2 and blinear_v3 are implemented from the referenced server-side format behavior and validated against the sample files.