ExtractEPW

Web-based tool for extracting assets.epw out of any WASM-GC based offline Eaglercraft HTML file.

https://kinnnine.github.io/extractepw

Notice

This project's source code doesn't host or contains any portion of Eaglercraft and any offline Eaglercraft HTML files. Its only job is allows you to extract assets.epw out of HTML file you provided.

Spaghetti code and bugs are expected to be found here, and not every html files will work with this tool.

Tested Eaglercraft HTML files

• EaglercraftX_1.8_u53_WASM-GC_Offline.html
  expected assets.epw sha256: ecfa438804724de30a871408058b25504746ab14705486cd9ec32855676cc524
• Eaglercraft_1.12.2_u3_WASM_Offline.html
  expected assets.epw sha256: 6dc65357ddc681ee95ec8623850de6389d746c723fb7329eb3f8746ffcbbafb3

Valid assets.epw file must have a magic number of 45 41 47 24 57 41 53 4D (|EAG$WASM|), hexdump output example below.

$ hexdump -n 8 -C assets.epw
00000000  45 41 47 24 57 41 53 4d                           |EAG$WASM|

How it works?

This tool's main function can break down into 4 steps:

1. Find the longest line containing base64 string, by using matching string window.eaglercraftXOpts.assetsURI.
   code
2. Now, we should have window.eaglercraftXOps.assetsURI = "data:application/octet-stream;base64,<huge_and_long_base64_string>==";, store it to somewhere.
   code
3. Take entire line of matched string into cleaning and stripping out the unneeded, we should have just a very long base64 string.
   code
4. Decode the base64 string into file data, then create a blob file for it, finally we will have assets.epw available for download.
   code

How to use

This tool is very straightforward, press Choose File, select valid .html file and then press Extract & Download.

Technologies used

• Mithril.js: JavaScript framework
• Workbox: Handling asset caching for offline use
• xterm.js: Logging
• Vite: Web Bundler

Credits

• lax1dude: Eaglercraft, inventing EPW file format.

Copyright and License

This software is created by Supphakit Duanghoy (kinnnine), copyright (c) 2026 under GPLv2 license.