Minecraft PE 0.8.1 Chunk Format Documentation

1. NBT Format (level.dat)

• File Type: Uncompressed little-endian NBT file.
• Header (8 bytes):
  • 4 bytes: Storage version (little-endian integer).
  • 4 bytes: Length of the file (excluding the header).

Important Tags:

• GameType:
  • 0 = Survival.
  • 1 = Creative.
• LastPlayed: Unix timestamp for the last save.
• LevelName: World name.
• Platform: Typically 2 (Bedrock).

Player Data:

• Armor: A list of 4 TAG_Compound values (helmet, chestplate, leggings, boots).
• Inventory:
  • id: Item or Block ID.
  • count: Number of items.
  • damage: Wear and tear on tools/armor.
  • slot: Inventory slot number.
• Abilities:
  • mayfly: 1 = Can fly.
  • invulnerable: 1 = Immune to damage.
  • mayBuild: 1 = Can place/destroy blocks.

World Data:

• SpawnX/SpawnY/SpawnZ: Spawn coordinates.
• Time: Tracks time of day in ticks (mod 19200).
• DayCycleStopTime: Stops the day/night cycle at specific ticks.
• RandomSeed: Seed for world generation.
• spawnMobs: 1 = Mob spawning enabled.

Compression:

• None (file is uncompressed).

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2. Chunk Data (chunks.dat)

Chunk Dimensions:

• 16×16×128 blocks (YZX - Y iterates first).
• Organized into 32×32 sections, storing up to 512×512×128 blocks.
• Default world generates 256 chunks.

File Structure:

• Divided into 4 KB sectors.
  • First sector: Chunk index (4 bytes per chunk).
    • 1st byte: Number of 4 KB sectors the chunk occupies.
    • Next 3 bytes: Chunk location (little-endian).
    • Example: 15 51 01 00 = Chunk starts at sector 337, taking 21 sectors.

Chunk Data Structure:

• Block Data (first 32,768 bytes): Block order is YZX (Y iterates first). Uses a 3D array: [16][16][128].
• Meta/Data (next 16,384 bytes): Auxiliary data (e.g., wool color, chest orientation).
  • Stored as half-byte per block (two blocks per byte).
• Skylight Data (next 16,384 bytes): Sunlight hitting blocks. Same format as block data.
• Blocklight Data (next 16,384 bytes): Light emitted by blocks (e.g., glowstone).
• Biome Data (last 256 bytes): Block order is ZX (Z iterates first). Biome info per block. Stored as 16 bytes per row.

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3. Entities (entities.dat)

• File Type: Modified little-endian NBT format.
• Header (12 bytes):
  • ASCII "ENT".
  • 1 zero byte.
  • 4-byte integer: Version (always 1).
  • 4-byte integer: Length of file (excluding header).

Entity Data:

• Entities List: Contains entity-specific NBT data.
  • Common Fields:
    • id: Entity type ID (e.g., Zombie = 32, Sheep = 13).
    • Pos: Position (X, Y, Z).
    • Motion: Velocity (dX, dY, dZ).
    • Rotation: Yaw and Pitch.
  • Mobs: Additional tags (e.g., Health, HurtTime, AttackTime, DeathTime).
  • Sheep: Special tags like Sheared and Color.
  • Item Entities: id, count, damage, age (time until despawn).

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4. File Format Changes

• Compression: None (uncompressed).
• Block Data Storage: Terrain, light data stored across multiple sections.
• Entities: Stored using an NBT-based structure, varies by entity type (e.g., mobs, items).

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5. Raw NBT Data

• InhabitedTime: Total time chunk has been loaded with players nearby.
• Entities: List of mobs, items, and other entities in the chunk.
• TileEntities: Data for blocks with extra information (e.g., chests, furnaces).
• Terrain Generation: Includes random seeds, feature generation flags.

Contributors

Dexrn ZacAttack

BJTMastermind

EternalModz

Changelog

Last edited 9 minutes ago

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77c2cb2-PreLoginPacket (also newlines might be fucked)

df6ba1d-Refactored Pi docs - Symlinked relevant files from the Bedrock docs as Pi's format is the same as PE 0.6.0

aa6927f-Added the initial Pi Edition docs