I’ve tried the small ones on GitHub Pages, but they usually miss undocumented instructions or only work for tiny code snippets.

For example, if a disassembler encounters the byte sequence 3E 42 , it translates it to: LD A, 42h Use code with caution.

: Modern JavaScript engines often process small-to-medium ROM files almost instantly. Popular Tools & Alternatives

Thanks!

If you are currently working on a retro computing project, let me know:

Supporting the main "unprefixed" instructions (like LD BC, nn or ADD A, B ) is easy. The difficulty lies in handling the exotic prefixes:

While many early systems ran on Z80 derivatives (e.g. the Game Boy's custom LR35902), the classic Z80's instruction set is rich and complex. Beyond the main opcodes, the CPU has four prefix bytes that dramatically alter how an instruction is decoded:

on how to use one of these online tools to disassemble a specific HEX file? GitHub - cormacj/z80-smart-disassembler