Getting Started with Udis86: Install, Build, and Use libudis86

Udis86: A Minimal x86/x86-64 Disassembler Library

Overview
Udis86 is a small, permissively licensed disassembler library for x86 and x86-64 machine code. It focuses on a compact API, low footprint, and easy embedding in projects that need instruction decoding without the complexity of larger frameworks.

Key features

• Supports 16/32/64-bit x86 instruction decoding.
• Small codebase and straightforward C API.
• Output options: textual mnemonics, raw instruction bytes, and decoded instruction metadata (opcode, operands, size).
• Streaming decode API suitable for parsing contiguous byte buffers.
• BSD-style license (permissive), easy to include in open-source or proprietary projects.
• Minimal dependencies — intended for lightweight use.

Typical uses

• Binary analysis and reverse engineering tools.
• Emulators and virtual machines needing instruction parsing.
• Debuggers, tracers, and instrumentation tools.
• Disassembly in build tools or static analysis pipelines.

Basic usage (conceptual)

1. Initialize a udis86 handle and set mode (16/32/64-bit).
2. Feed a buffer or set a program counter.
3. Call the decode function to retrieve each instruction’s mnemonic, length, and operand info.
4. Optionally format output as text for human-readable disassembly.

Strengths

• Very small and simple to integrate.
• Fast enough for many offline and lightweight runtime uses.
• Straightforward API for quick prototyping.

Limitations

• Less feature-rich than larger disassemblers (e.g., Capstone): fewer convenience features, less extensive instruction metadata, and fewer language bindings.
• Not actively maintained to the extent of larger projects (check current repo status before relying on it for long-term projects).

Where to get it

• Source and documentation are available from the project’s repository (search for libudis86 / udis86) — check the repo for the latest releases and build instructions.

February 7, 2026