RePack — Eaglercraft Save Editor

Status: Beta

This project is still under active development. Expect bugs, rough edges, and incomplete features. If you are not comfortable troubleshooting issues on your own, you may want to wait for a more stable version.

If you are interested in helping improve the project—especially usability and simplicity—contributions are welcome. Reach out (snap): @ayqshi

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What This Project Is

RePack is a browser-based tool for inspecting, editing, and rebuilding .epk save files used in Eaglercraft.

It is designed for users who want more control over their world data—whether that means exploring file contents, modifying NBT data, or understanding how .epk archives are structured internally.

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Features

EPK Extraction

Decompile .epk archives and access their internal files.

• View the full contents of a save
• Understand file structure and layout
• No external tools required

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NBT Parsing (Readable JSON)

Automatically converts .dat (NBT) files into structured JSON.

• Makes complex binary data readable
• Easier inspection of player and world data
• Simplifies editing workflows

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File Editing

Edit supported file types directly in the browser:

• JSON (NBT data)
• Plain text files

Changes are applied in real time and reflected in the repacked archive.

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EPK Repacking

Rebuild a valid .epk archive after making edits.

• Preserves original structure
• Automatically re-compresses files when required (GZIP)
• Designed to minimize manual intervention

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Integrity Checks

Basic validation is included to reduce the chance of corruption:

• Header and footer verification
• CRC32 checks for file data consistency

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Binary File Handling

Files that cannot be displayed are still preserved:

• Shown as placeholders in the UI
• Included unchanged during repacking

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Usage

1. In Eaglercraft:

   • Select your world
   • Click Backup and export as .epk

2. In RePack:

   • Open the tool (beta)
   • Upload your .epk file

3. Browse and edit:

   • Select a file from the extracted list
   • Its contents will appear in the editor panel

4. Repack:

   • Save your changes
   • Download the rebuilt .epk file

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How It Works

RePack runs entirely in your browser using JavaScript. Files are processed locally and are not uploaded to any server.

EPK Format Overview

An .epk archive contains:

• A header

• Version information

• File count (stored as Big-Endian)

• A metadata table for each file:

  • Name
  • Size
  • Offset
  • Compression type
  • CRC32 checksum

• File data blocks

• A footer

Most numeric values are stored as Little-Endian, except for the file count, which uses Big-Endian encoding.

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Internal Processing

When loading a file:

• The archive structure is parsed
• Metadata and offsets are read
• Files are decompressed if necessary
• NBT data is converted into JSON

When repacking:

• Metadata is rebuilt
• Files are recompressed where required
• CRC32 values are recalculated
• A valid .epk archive is generated

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Dependencies

• Pako.js — GZIP compression and decompression
• NBT.js — Parsing and handling NBT data

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Limitations

• Some edge cases may fail during extraction or repacking
• User interface is minimal and still evolving
• Binary files cannot be edited
• Error handling is not yet comprehensive

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Contributing

Feedback and contributions are encouraged, especially in areas like:

• Simplifying the user experience
• Improving error handling
• Expanding file support

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Notes

This tool is intended for users who want direct access to and control over their save data. It prioritizes transparency and functionality over polish at this stage of development.