World Pruning

Optimize world size by selectively keeping or removing regions during conversion

Overview

World pruning allows you to selectively keep or remove specific regions of your world during conversion. This is useful for:

• Reducing world file size
• Removing unused or unwanted areas
• Keeping only specific regions (spawn area, builds, etc.)
• Creating smaller test worlds

Configuration File

Pruning is configured via pruning.chunker.json placed in your world folder or specified with the -p flag.

File Structure

The pruning configuration uses a dimension-based structure (DimensionPruningList.java:1-33, CLI.java:196-210):

pruning.chunker.json

{
  "configs": [
    {
      "include": true,
      "regions": [
        {
          "minChunkX": -10,
          "minChunkZ": -10,
          "maxChunkX": 10,
          "maxChunkZ": 10
        }
      ]
    },
    null,
    null
  ]
}

The configs array is ordered by dimension: [OVERWORLD, NETHER, THE_END] (Dimension.java:19-23).

Dimension Order

The configs array follows Minecraft’s dimension order:

• Index 0: Overworld (minecraft:overworld)
• Index 1: Nether (minecraft:the_nether)
• Index 2: The End (minecraft:the_end)

Use null for dimensions you don’t want to prune. Missing dimensions or null values mean no pruning will occur.

Configuration Fields

Pruning Config

include · boolean · default: "true"

Whether to include or exclude the specified regions (PruningConfig.java:10, 33-37)

• true: Keep only the specified regions (remove everything else)
• false: Remove the specified regions (keep everything else)

regions · array

Array of regions to keep or remove (PruningConfig.java:11, 40-46)

Pruning Region

Each region defines a rectangular area in chunk coordinates (PruningRegion.java:1-69):

minChunkX · integer

Minimum chunk X coordinate (PruningRegion.java:7, 38-40)

minChunkZ · integer

Minimum chunk Z coordinate (PruningRegion.java:8, 46-49)

maxChunkX · integer

Maximum chunk X coordinate (PruningRegion.java:9, 54-57)

maxChunkZ · integer

Maximum chunk Z coordinate (PruningRegion.java:10, 62-65)

Examples

Keep Only Spawn Area

Keep a 20x20 chunk area around spawn (320x320 blocks):

pruning.chunker.json

{
  "configs": [
    {
      "include": true,
      "regions": [
        {
          "minChunkX": -10,
          "minChunkZ": -10,
          "maxChunkX": 10,
          "maxChunkZ": 10
        }
      ]
    },
    null,
    null
  ]
}

"include": true means only the specified region will be kept. Everything outside will be removed.

Remove Griefed Area

Remove a specific area that was griefed:

pruning.chunker.json

{
  "configs": [
    {
      "include": false,
      "regions": [
        {
          "minChunkX": 50,
          "minChunkZ": 50,
          "maxChunkX": 100,
          "maxChunkZ": 100
        }
      ]
    },
    null,
    null
  ]
}

"include": false means the specified region will be removed. Everything else will be kept.

Multiple Regions

Keep multiple separate areas:

pruning.chunker.json

{
  "configs": [
    {
      "include": true,
      "regions": [
        {
          "minChunkX": -10,
          "minChunkZ": -10,
          "maxChunkX": 10,
          "maxChunkZ": 10
        },
        {
          "minChunkX": 100,
          "minChunkZ": 100,
          "maxChunkX": 150,
          "maxChunkZ": 150
        }
      ]
    },
    null,
    null
  ]
}

Prune Multiple Dimensions

Prune both Overworld and Nether:

pruning.chunker.json

{
  "configs": [
    {
      "include": true,
      "regions": [
        {
          "minChunkX": -20,
          "minChunkZ": -20,
          "maxChunkX": 20,
          "maxChunkZ": 20
        }
      ]
    },
    {
      "include": true,
      "regions": [
        {
          "minChunkX": -5,
          "minChunkZ": -5,
          "maxChunkX": 5,
          "maxChunkZ": 5
        }
      ]
    },
    null
  ]
}

Prune Only The End

Keep only a small End area, leave other dimensions untouched:

pruning.chunker.json

{
  "configs": [
    null,
    null,
    {
      "include": true,
      "regions": [
        {
          "minChunkX": 0,
          "minChunkZ": 0,
          "maxChunkX": 10,
          "maxChunkZ": 10
        }
      ]
    }
  ]
}

Coordinate System

Understanding Chunk Coordinates

Chunks are 16x16 block areas. To convert block coordinates to chunk coordinates:

chunkX = floor(blockX / 16)
chunkZ = floor(blockZ / 16)

Example Conversion

If you want to keep blocks from (-160, 64, -160) to (160, 320, 160):

minChunkX = floor(-160 / 16) = -10
minChunkZ = floor(-160 / 16) = -10
maxChunkX = floor(160 / 16) = 10
maxChunkZ = floor(160 / 16) = 10

The Y coordinate (height) is not used in pruning. Pruning removes entire vertical columns of chunks.

Usage

World Folder

# Place in world directory
my_world/pruning.chunker.json

# Run conversion
java -jar chunker-cli.jar -i my_world -f BEDROCK_1_20_80 -o output

Region Selection Strategies

Include Strategy (Whitelist)

When "include": true:

• Chunks inside defined regions are kept
• Chunks outside defined regions are removed
• Best for: Keeping specific areas (spawn, builds, etc.)

Exclude Strategy (Blacklist)

When "include": false:

• Chunks inside defined regions are removed
• Chunks outside defined regions are kept
• Best for: Removing unwanted areas (grief, corruption, etc.)

Performance Considerations

Pruning is performed during the read phase of conversion, so pruned chunks are never processed. This saves:

• Conversion time
• Memory usage
• Output file size

File Size Reduction

Pruning can significantly reduce world size:

• Small spawn area: 90-95% size reduction
• Multiple regions: 50-80% size reduction
• Removing unused dimensions: 30-60% size reduction

Best Practices

1. Always backup your world before pruning
2. Test first with a copy of your world
3. Use visualization tools to identify chunk coordinates
4. Buffer regions by 1-2 chunks to avoid cutting off structures
5. Check dimension IDs to ensure correct pruning order

Visualization Tools

To help identify regions to prune:

• Minecraft: Press F3+G to show chunk boundaries
• External tools: Use MCA Selector, Amulet, or similar
• Coordinates: F3 shows both block and chunk coordinates

Common Use Cases

Server Spawn

Keep only spawn and hub areas for smaller server worlds

Mini-games

Extract specific arenas or game areas

Showcases

Create compact worlds featuring specific builds

Testing

Generate small test worlds from production servers

Troubleshooting

Wrong area removed

• Verify chunk coordinates (not block coordinates)
• Check include vs exclude logic
• Ensure dimension order is correct

Nothing pruned

• Check that configs array is not empty
• Verify regions array has entries
• Ensure dimension index matches intended dimension

Conversion fails with pruning error

• Validate JSON syntax
• Ensure minChunk values are less than maxChunk values
• Check that configs array has exactly 3 elements or fewer

Structure cut off

• Expand region boundaries by 1-2 chunks
• Structures can span multiple chunks
• Check if structure extends beyond defined region

Empty Configs

An empty configs array means no pruning:

{
  "configs": []
}

This is equivalent to not having a pruning configuration file.

Related

Configuration Overview

Learn about all configuration options

Converter Settings

Control what gets converted

Dimension Mapping

Map dimensions between editions