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Overview

The Chunker desktop application provides a user-friendly interface for converting Minecraft worlds between Java and Bedrock editions. Built with Electron, it offers an intuitive step-by-step workflow with advanced customization options.

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Installation

  1. Download the appropriate version for your operating system from the releases page
  2. Extract the archive (if applicable)
  3. Run the Chunker executable:
    • Windows: Chunker.exe
    • macOS: Chunker.app
    • Linux: Chunker or Chunker.AppImage

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Memory Configuration

Chunker defaults to using 75% of your available system memory. You can customize this: 
# Windows
Chunker.exe -Xmx8G

# macOS/Linux
./Chunker -Xmx8G
For additional JVM options: 
Chunker.exe --java-options="-Xmx8G -Xms4G"
The -Xmx and -Xms flags are forwarded to the backing JVM. Use --java-options for other JVM parameters.

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Conversion Workflow

The app guides you through a multi-step process to convert your world:

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Step 1: Select World

Choose your Minecraft world using one of three methods:
Click Choose world folder and navigate to your world directory. The folder must contain a level.dat file.Common world locations:
  • Java: %appdata%/.minecraft/saves/ (Windows) or ~/Library/Application Support/minecraft/saves/ (macOS)
  • Bedrock: %localappdata%/Packages/Microsoft.MinecraftUWP_8wekyb3d8bbwe/LocalState/games/com.mojang/minecraftWorlds/ (Windows)
After selecting a world, Chunker will:
  1. Prepare the world files
  2. Detect the Minecraft version automatically
  3. Display the detected version and available conversion options

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Step 2: Export As

Select the target Minecraft version for your converted world. The available versions are displayed with the most recent at the top. Your current version is marked as “source”.
Convert - Quick conversion with default settingsAdvanced Mode - Access to advanced settings including:
  • World preview
  • Custom block mappings
  • World settings modification
  • Dimension pruning
  • Converter settings

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Step 3: Advanced Settings (Optional)

If you selected Advanced Mode, you’ll access a settings panel with multiple tabs:

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World Preview

View a 2D or 3D preview of your world before conversion. This helps you verify that the correct world was selected.

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World Settings

Modify world properties such as:
  • World name
  • Game mode (Survival, Creative, Adventure)
  • Difficulty (Peaceful, Easy, Normal, Hard)
  • Spawn point coordinates
  • Game rules
  • Weather settings
Changes to world settings will override the original values in the converted world.

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Dimensions/Pruning

Control which dimensions and regions to include in the conversion:
  • Dimension Selection: Choose which dimensions to convert (Overworld, Nether, End)
  • Pruning: Define coordinate ranges to exclude specific chunks from conversion
  • Benefits: Reduce conversion time and output world size
Example use case: Convert only the spawn area of a large world: 
{
  "Overworld": {
    "minX": -1000,
    "maxX": 1000,
    "minZ": -1000,
    "maxZ": 1000
  }
}

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Block Mapping

Customize how specific blocks are converted:
  • Search for blocks by name or ID
  • View default mappings
  • Create custom block mappings
  • Override default conversion behavior
Example: Map all Java Edition granite to Bedrock Edition diorite instead of the default mapping.

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Converter Settings

Fine-tune the conversion process:
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customIdentifiers
boolean
default:"true"
Passthrough Custom IdentifiersAllow custom identifiers outside the minecraft namespace to be read/written. Disable to prevent modded blocks from being converted.
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blockConnections
boolean
default:"true"
Calculate Block Connections Using NeighboursUse neighboring chunks to determine block connections (fences, chests, panes). Improves accuracy but may slow conversion.
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itemConversion
boolean
default:"true"
Convert ItemsEnable conversion of items in chests, inventories, and other containers.
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lootTableConversion
boolean
default:"true"
Convert Structure Loot TablesAttempt to match and convert structure loot table files.
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mapConversion
boolean
default:"true"
In-Game Map ConversionConvert in-game map items and their data.
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discardEmptyChunks
boolean
default:"false"
Discard Empty ChunksDon’t write chunks that contain no blocks. Reduces output world size.
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preventYBiomeBlending
boolean
default:"false"
Prevent Y Biome BlendingRequire an empty chunk at the top of each column to prevent vertical biome blending (Java Edition only).
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enableCompact
boolean
default:"true"
Enable LevelDB Compact (Bedrock only)Compact the LevelDB database at the end of conversion. May increase conversion time but optimizes the output world.
Exporting Settings
You can export your settings for reuse:
Click Save .zip to download a ZIP file containing:
  • world_settings.chunker.json
  • converter_settings.chunker.json
  • block_mappings.chunker.json
  • pruning.chunker.json
  • dimension_mappings.chunker.json
Place these files in the same directory as your world’s level.dat to automatically load them when selecting the world in Chunker.

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Step 4: Processing

The conversion process begins after you click Convert. 
Converting from Java Edition 1.20.5 to Bedrock Edition 1.20.80
▓▓▓▓▓▓▓▓▓▓░░░░░░░░░░ 50.00%
Progress is displayed with:
  • Source and target versions
  • Real-time progress percentage
  • Estimated time remaining (when available)
For Bedrock conversions with compaction enabled: 
Compacting world, this may take a while...
Large worlds may take several minutes to convert. Don’t close Chunker during this process.

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Step 5: Save World

Once conversion completes, you can save the converted world:
  1. Click Save to choose where to save the converted world
  2. The world is packaged as:
    • .zip archive for Java Edition
    • .mcworld or folder for Bedrock Edition

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Conversion Logs

If there were any issues during conversion:
  • Errors: Error IDs are displayed for support purposes
  • Missing Identifiers: Click Show Output Log to view blocks that couldn’t be mapped
Missing identifiers occur when a block in the input world doesn’t have a mapping to the output format. This is common for:
  • Modded blocks
  • Blocks from newer versions not yet supported
  • Custom blocks from resource packs
These blocks are typically converted to air or a similar block.
After saving, click Restart to convert another world.

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Features

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Automatic Version Detection

Chunker automatically detects the Minecraft version of your world by analyzing the world files. No manual version selection required.

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Drag and Drop Support

Simply drag world folders or archive files into the Chunker window to begin the conversion process.

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Cross-Platform

Available for Windows, macOS, and Linux with native executables for each platform.

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World Preview

Visualize your world before conversion to ensure you’ve selected the correct world.

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Batch Processing

While the GUI doesn’t support batch processing directly, you can use the CLI for automated batch conversions.

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Troubleshooting

The desktop app uses a Java backend process. If this error occurs:
  • Ensure Java 17+ is installed on your system
  • Try closing and reopening Chunker
  • Check if antivirus software is blocking the process
  • Verify you have sufficient memory available
This occurs when the selected folder doesn’t contain a valid level.dat file:
  • Ensure you’re selecting the world folder, not a parent directory
  • Verify the world isn’t corrupted
  • Try selecting the world using a different method (archive vs folder)
If Chunker runs out of memory:
  • Launch Chunker with more memory: Chunker.exe -Xmx16G
  • Use dimension pruning to reduce the conversion size
  • Close other applications to free up RAM
  • Try converting on a machine with more memory
If using Bedrock output with compaction enabled, the compaction phase can take several additional minutes. Wait for the “Finished compacting world” message.
Possible causes:
  • Incompatible NBT data (if using Keep Original NBT)
  • Unsupported blocks in the source world
  • Corrupted conversion output
Try:
  • Converting again without custom settings
  • Disabling Keep Original NBT if enabled
  • Checking the output log for missing identifiers

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Limitations

The following features have limited or no conversion support:
  • Entities: Only paintings and item frames are converted. Other entities (mobs, armor stands, etc.) are not converted.
  • Structure Data: Village, stronghold, and other structure data is not preserved.
For more details on supported features, see the Chunker README.

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See Also

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