Since React Native 0.60.4 developers can opt-in to use the Hermes JS Engine. This generates an index.android.bundle binary that contains Hermes JS bytecode.

The Hermes documentation mentions hbcdump which is described as a "Hermes bytecode disassembler"

By using hbcdump -pretty-disassemble -c disassemble -out out.txt index.android.bundle I do get something that is at least a little more human readable but it does not look like it can be compiled back again and is not easy to work with.

How can I decompile Hermes JS bytecode into JavaScript?
Alternatively: How can I modify the bytecode? Is there a tool that understands this bytecode?

2 Answers 2


My friend made this tool: hbctool, a Hermes bytecode disassembler/assembler.

This will help you disassemble the file into a more readable format (similar to hbcdump), so you can modify and re-assemble it.

  • 2
    Is there any way to decompile the bytecode to readable javascript?
    – user37355
    Jun 25, 2021 at 10:56
  • 1
    It only supports older versions of HBC unfortunately Jun 2, 2022 at 0:28

Refer below link someone added support for version 84 in his forked repo



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