MCA JSON

MCA JSON is a free toolkit for converting, inspecting, and editing Minecraft Java Edition world files through command-line utilities or a typed JavaScript library. It is aimed at developers and technically minded world owners who need direct file-level control rather than a visual editor. Its broad format support and focused maintenance commands are useful, although large regions and unusual compression require care.

Overview

MCA JSON works with MCA (Anvil), NBT, and SNBT data from Minecraft Java Edition. You can run its command-line tools for one-off operations or use the TypeScript library inside a larger application. That makes it a practical foundation for scripts, migration utilities, diagnostics, and targeted world repairs. Bedrock Edition is not supported because it uses a different format, so Bedrock users need another tool.

Key features

The command-line tools convert MCA and NBT files to JSON and convert JSON back to those formats. They can list chunks, find signs, remove chunks, and read player locations, giving administrators useful ways to inspect or clean a world without building their own parser. These commands suit maintenance jobs and automation; they are not a substitute for a graphical terrain or inventory editor.

The TypeScript library supplies typed classes and methods for parsing and modifying MCA files, NBT files, and SNBT strings. Global and project installation are documented with npm, while Deno, Bun, pnpm, and other package managers can also be used. The package is ES-modules-only. It has no Node-specific tooling requirement for browser bundles, while Node.js applications require version 20 or newer. Developers targeting older Node releases will need to update their runtime or choose another library.

Region structure and NBT reading are reported across Minecraft versions from 1.2.1 through 1.21. Chunk readers handle zlib, gzip, LZ4, and uncompressed data, but edited chunks are written with zlib. Chunks larger than 1 MiB that live in separate .mcc files, along with chunks using custom compression, cannot be read. They can still be listed and removed, which preserves some administrative value but limits full inspection and editing of those regions.

JSON output can become very large: a mostly untouched example region produced about 1 GB. Compact and condensed output modes help reduce that burden, but users should still plan storage and processing capacity before converting broad areas.

Pricing

MCA JSON costs nothing under its single free plan. It includes the open-source command-line tools and JavaScript library, with no paid tier or trial requirement. This is a strong fit for hobbyists, server operators, and developers who can manage files or code themselves; there is no commercial support or higher tier described for teams needing different service terms.

Platforms

The software is available on Linux, macOS, Windows, and the web. The browser option follows from the library's ability to bundle without Node-specific tooling, while command-line and Node use remain suited to local or server-side workflows. ES modules-only packaging should be checked against an existing build system.

Who it's for

Choose MCA JSON if you need programmable access to Java world data, repeatable conversions, chunk-level cleanup, or typed parsing in a JavaScript or TypeScript project. It is particularly appropriate for technically confident world owners and developers building browser or server utilities. It is a poor match for Bedrock worlds, users who require a visual editor, or jobs centered on unreadable oversized or custom-compressed chunks.

Pros and cons

• Pros: Free command-line and library tooling covers conversion, inspection, and modification.
• Pros: Typed APIs support MCA, NBT, and SNBT workflows, with browser bundling and broad package-manager installation options.
• Pros: Reads several compression formats and reports compatibility efforts spanning Java 1.2.1 to 1.21.
• Cons: Bedrock Edition is excluded.
• Cons: Oversized .mcc chunks and custom compression cannot be read, and modified data is saved with zlib.
• Cons: JSON conversion can generate roughly 1 GB for an example region, demanding careful output management.

Alternatives

For a broader visual starting point, browse Minecraft World Editors. MCBE Inventory Editor is the better free choice when Bedrock inventory work is the priority, with Linux, macOS, self-hosted, web, and Windows support. Choose Chunker instead for a free, MIT-licensed open-source tool from Hive Games. Bedrock NBT Editor fits free Bedrock NBT editing on Android, iOS, or the web.

biomed is a free MIT-licensed alternative for Linux, macOS, and Windows. LiveNBTEditor targets Minecraft Java 26.3 and requires a Windows editor, while MCA Selector offers free MIT-licensed downloadable builds for Windows, macOS, Linux, and universal Java. McpeTool is another free MIT-licensed option across API, Linux, macOS, self-hosted, and Windows environments. Minecraft Region Fixer is worth considering for GPL-3.0 region repair on Linux, macOS, or Windows with Python 3.x.

Verdict

MCA JSON is the right pick for Java Edition users who want free, scriptable control over MCA, NBT, and SNBT files, especially when typed JavaScript APIs or focused chunk operations matter. Its main reason to look elsewhere is equally clear: visual editors, Bedrock support, and complete handling of oversized or custom-compressed chunks are outside its practical scope.