What is the MCA file format?
Files with the .mca extension belong to the Game Files category and store world data for Minecraft Java Edition.
What do MCA files contain?
The contents of files with the .mca extension are world chunk data for the game Minecraft. Players can build their own communities, modify locations, and interact with other users within them. The files store all elements of the Minecraft universe, such as:
- blocks, from which structures are built,
- terrain, biomes, and buildings,
- player characters and other entities,
- items and tools.
Files with the .mca extension replaced the previous Minecraft map standard .mcr when Java Edition 1.2.1 launched on 1 March 2012.
What are MCA files used for?
The Anvil world save format offers more functionality than its MCR predecessor. The main improvements concerned reducing the data overhead per chunk, which contributed to relieving Minecraft servers. Thanks to the changed internal structure, chunk compression was noticeably improved - zlib DEFLATE by default, with LZ4 support added in Java Edition 1.20.5. Each .mca file covers a 32×32 chunk region (512×512 blocks), named r.X.Z.mca by region coordinates, and stores up to 1,024 chunk slots.
Java Edition 1.18 expanded world height to Y=-64 through Y=320, adding deeper underground terrain and higher build limits. Special features of the Anvil format - palette-indexed block states since the 1.13 Flattening update and per-chunk DataVersion tags - offer wide possibilities for modifying and analysing game worlds. Bedrock Edition worlds use LevelDB instead of .mca files.
Security & safety
RISK: LOWMCA files are pure binary data files with no executable code. Safe to copy, backup, and open with NBT tools. Risk: editing chunk data incorrectly can corrupt a Minecraft world; always back up saves/ before editing. Never download world files from untrusted sources as they may contain intentionally corrupted data designed to crash clients.
Format details
in a nutshellPrograms that open MCA files
Windows5 apps
NBTExplorer
Open-source File > Open; browse the chunk tree in region files. Older tool; NBT Studio is the updated successor. 
Minecraft (Java Edition)
Paid MCA files are opened automatically when Minecraft loads a world from the saves/ folder. Place world folder under %APPDATA%\.minecraft\saves\.
NBT Studio
Open-source File > Open; select an .mca file to browse chunk tree, inspect/edit NBT tags within region chunks. Successor to NBTExplorer.
Chunker (Hive Games)
Free Web-based tool: upload Java Edition world ZIP; view/convert to Bedrock Edition. Handles MCA region files.
Amidst
Open-source Load a Minecraft world folder to render a top-down biome/structure map by reading MCA files. 
macOS2 apps
Minecraft (Java Edition)
Paid MCA files loaded automatically from ~/Library/Application Support/minecraft/saves/. 
Linux2 apps
Minecraft (Java Edition)
Paid MCA files loaded automatically from ~/.minecraft/saves/ when launching a world.
Chunker (Hive Games)
Free Upload Java Edition world ZIP; view map tiles, convert to Bedrock Edition format. Technical details
deep spec| Binary encoding | Big-endian |
| Header size | 8,192 bytes (two 4,096-byte lookup tables) |
| Chunk slots per file | 1,024 (32×32 region grid) |
| Chunk payload format | NBT (Named Binary Tag) |
| Default compression | zlib DEFLATE (type 2) |
| Legacy compression | GZip (type 1) |
| LZ4 compression | Type 4, added in Java Edition 1.20.5 (2024) |
| World coverage per file | 32×32 chunks = 512×512 blocks horizontally |
| World height (Java 1.18+) | Y=-64 to Y=320 (26 vertical chunk sections) |
| File naming convention | r.X.Z.mca where X, Z are region coordinates |
| Chunk format tracker | DataVersion NBT tag per chunk |
| Block storage (since 1.13) | Palette-indexed long arrays |
| Bedrock Edition | Not applicable - Bedrock Edition uses LevelDB, not .mca files |
| Released | 2012 (Minecraft Java Edition 1.2.1, March 1, 2012 - replaced MCR format) |
| Latest version | Anvil (1.2.1, 2012); Linearized variant in Minecraft 1.21 (2024) for some data |
| Specification | minecraft.wiki |
MCA conversions
Community Q&A
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