What is kaitai_struct?

kaitai-io/kaitai_struct — explained in plain English

Analysis updated 2026-06-26

★ 4,599ShellAudience · developerComplexity · 3/5Setup · moderate

Mindmap

mindmap
  root((Kaitai Struct))
    What It Does
      Describe binary formats
      Generate parsers
      Cross-language output
    Workflow
      Write .ksy file
      Compile with KSC
      Add runtime library
      Use generated class
    Output Languages
      Python
      Java
      Go
      Rust
      JavaScript
    Use Cases
      Image file parsing
      Network packet parsing
      Custom app formats
    Audience
      Developers
      Reverse engineers

mindmap root((Kaitai Struct)) What It Does Describe binary formats Generate parsers Cross-language output Workflow Write .ksy file Compile with KSC Add runtime library Use generated class Output Languages Python Java Go Rust JavaScript Use Cases Image file parsing Network packet parsing Custom app formats Audience Developers Reverse engineers

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What do people build with it?

USE CASE 1

Write a single .ksy description file for a custom binary format and generate parsers for Python, Java, and Go without duplicating logic.

USE CASE 2

Use a pre-built format description from Kaitai's format library to parse common file types like images or audio without writing parser code.

USE CASE 3

Validate that a new binary format description parses correctly using the Kaitai Struct visualizer before generating code.

USE CASE 4

Share one format definition across a cross-language team so each member gets a generated parser in their own language.

What is it built with?

ShellPythonJavaGoRubyRustC++JavaScript

How does it compare?

	kaitai-io/kaitai_struct	security-onion-solutions/securityonion	eooce/sing-box
Stars	4,599	4,605	4,591
Language	Shell	Shell	Shell
Setup difficulty	moderate	hard	moderate
Complexity	3/5	4/5	3/5
Audience	developer	ops devops	ops devops

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · moderate Time to first run · 30min

Requires installing the Kaitai Struct compiler and the small runtime library for your chosen target language.

No license information was provided in the explanation, check the repository directly.

So what is it?

Kaitai Struct is a tool for reading and parsing binary file formats: the kind of files that store data as raw bytes rather than readable text. Things like image files, audio files, network packet data, or custom application formats all fall into this category, and working with them normally requires writing tedious, error-prone code by hand in whatever programming language you happen to be using. The core idea is that instead of writing a parser in each language you need, you describe the binary format once in a dedicated description language using a .ksy file. That file acts as a blueprint: it lists the fields in the format, their types, sizes, and relationships. From this single description, the Kaitai Struct compiler generates ready-to-use parser code in whichever programming language you choose. The supported target languages include C++, C#, Go, Java, JavaScript, Lua, Nim, Perl, PHP, Python, Ruby, and Rust. This cross-language output means a format described once can be used by teams working in completely different technology stacks, without anyone rewriting the same parsing logic. The workflow is straightforward. You write a .ksy description file, optionally use a visualizer tool to confirm the format is being parsed correctly, then compile it into source code for your language. A small runtime library is added to your project alongside the generated code, and from there you call the generated class to read binary data. The project also maintains a collection of pre-written format descriptions for common file types. The main GitHub repository is an umbrella hub that links to individual component repositories, contributors are directed to fork the specific component they want to change rather than this top-level repo. Kaitai Struct suits developers who regularly deal with binary data parsing and want a single source of truth for format definitions.

Copy-paste prompts

Prompt 1

I have a custom binary file format with a 4-byte header, a 2-byte length field, and a variable-length data payload. Help me write a .ksy Kaitai Struct description for it.

Prompt 2

Generate a Python parser from my Kaitai .ksy format description. What compiler command do I run and what runtime library do I need?

Prompt 3

I want to parse PNG image files in Go using Kaitai Struct. Is there an existing .ksy for PNG, and how do I compile it to Go code?

Prompt 4

Show me how to set up Kaitai Struct in a Java Maven project to parse a custom binary network protocol format.

Frequently asked questions