Online Disassembler and Assembler

English | 中文 | Live Demo

A pure frontend online disassembler and assembler supporting multiple CPU architectures. All processing is done locally in the browser, no server required.

Features

• Disassembler - Convert machine code to assembly instructions
• Assembler - Convert assembly code to machine code
• Support for multiple architectures: ARM, ARM64, MIPS, x86, PowerPC, SPARC, SystemZ, XCore
• Little-Endian and Big-Endian support
• Multiple modes: 16-bit, 32-bit, 64-bit, ARM, Thumb, etc.
• x86 syntax support: Intel, AT&T, NASM, MASM, GAS
• Real-time results with copy functionality
• Dark/Light theme (auto-detect browser preference)
• Multilingual support (English/Chinese)
• Responsive design

Screenshots

Usage

Disassembler

1. Select architecture (ARM, ARM64, MIPS, x86, etc.)
2. Select endianness (Little-Endian or Big-Endian)
3. Select mode (16-bit, 32-bit, 64-bit, ARM, Thumb, etc.)
4. Enter machine code in hexadecimal format
5. Click "Disassemble" button
6. Copy results if needed

Assembler

1. Select architecture
2. Select endianness and mode
3. Select syntax (x86 only)
4. Enter assembly code (one instruction per line)
5. Click "Assemble" button
6. Copy generated machine code

Input Formats

Disassembler (Hex Input)

Supports multiple formats:

• Space-separated: 55 31 D2 89 E5
• Continuous: 5531D289E5
• Line-separated:

  55
  31 D2
  89 E5
  

Assembler (Assembly Code)

One instruction per line:

push rbp
xor edx, edx
mov ebp, esp
mov eax, dword ptr [rbp+8]

Technology Stack

• Capstone.js - Multi-architecture disassembly framework
• Keystone.js - Multi-architecture assembler engine
• Pure HTML/CSS/JavaScript (no frameworks)
• No backend required

Browser Support

• Chrome (recommended)
• Firefox
• Safari
• Edge

Local Development

1. Clone the repository

   git clone https://github.com/secnotes/onlineasm.git
   cd onlineasm

2. Open index.html in your browser

No build process or dependencies required.

File Structure

onlineasm/
├── index.html          # Main application
├── capstone.min.js     # Capstone disassembler library
├── keystone.min.js     # Keystone assembler library
├── README.md           # English README
└── README_CN.md        # Chinese README

License

MIT License

Credits

• Capstone - The ultimate disassembler
• Keystone - The assembler engine
• Capstone.js - JavaScript port of Capstone
• Keystone.js - JavaScript port of Keystone

Author

Security Notes