# Binaryen — WebAssembly Compiler and Optimization Toolchain

> A compiler infrastructure and toolchain library for WebAssembly that provides optimization, code generation, and interpretation in a single C++ library.

## Install

Save in your project root:

# Binaryen — WebAssembly Compiler and Optimization Toolchain

## Quick Use
```bash
# Install via package manager
# macOS
brew install binaryen

# Ubuntu/Debian
apt install binaryen

# Optimize a .wasm file
wasm-opt -O3 input.wasm -o output.wasm

# Convert WAT text format to binary
wasm-as module.wat -o module.wasm
```

## Introduction
Binaryen is a compiler and toolchain infrastructure library for WebAssembly, developed under the official WebAssembly GitHub organization. It provides a C/C++ API for generating, optimizing, and transforming WebAssembly modules. Binaryen powers the optimization pipeline of Emscripten and is used by multiple language compilers targeting WebAssembly.

## What Binaryen Does
- Optimizes WebAssembly modules with configurable pass pipelines (wasm-opt)
- Converts between WAT (text) and WASM (binary) formats
- Provides a C API for building WebAssembly modules programmatically
- Includes a WebAssembly interpreter for testing without a browser
- Merges, splits, and transforms WebAssembly modules

## Architecture Overview
Binaryen represents WebAssembly programs as an AST-based intermediate representation (IR). The optimizer runs a configurable pipeline of passes over this IR, including dead code elimination, inlining, constant folding, and memory optimization. The IR can be lowered to binary WebAssembly or printed as WAT text. A built-in interpreter executes the IR directly for validation and testing.

## Self-Hosting & Configuration
- Install via Homebrew, apt, or build from source with CMake
- Use wasm-opt as a standalone CLI for optimizing any .wasm file
- Integrate the C API (binaryen-c.h) into compiler backends
- Configure optimization levels from -O0 (none) to -Oz (size-optimized)
- Enable specific passes individually for fine-grained control

## Key Features
- Production-grade optimizer that typically reduces wasm binary size by 10-30%
- Used by Emscripten, AssemblyScript, Kotlin/Wasm, and other compiler toolchains
- Fast parallel compilation and optimization pipeline
- Support for all WebAssembly proposals including SIMD, threads, and GC
- Fuzzer and validator tools for testing WebAssembly modules

## Comparison with Similar Tools
- **wasm-tools (Bytecode Alliance)** — focuses on parsing and validation; Binaryen provides deeper optimization
- **Wabt** — a simpler toolkit for format conversion; Binaryen includes a full optimization pipeline
- **LLVM WebAssembly backend** — generates wasm from LLVM IR; Binaryen optimizes the output further downstream
- **wasm-pack** — Rust-specific build tool; Binaryen is language-agnostic and used as a post-processing step

## FAQ
**Q: Should I use wasm-opt on all my WebAssembly output?**
A: Generally yes. Running wasm-opt -O3 or -Oz after your compiler typically reduces binary size and improves runtime performance.

**Q: Does Binaryen support the WebAssembly GC proposal?**
A: Yes. Binaryen tracks WebAssembly proposals and supports GC types, reference types, and other in-progress specifications.

**Q: Can I use Binaryen from JavaScript?**
A: Yes. Binaryen provides binaryen.js, a compiled-to-JS version of the library that runs in Node.js or the browser.

**Q: How does Binaryen relate to Emscripten?**
A: Emscripten uses Binaryen as its WebAssembly optimization backend. When you compile C/C++ with Emscripten, wasm-opt runs automatically.

## Sources
- https://github.com/WebAssembly/binaryen
- https://webassembly.github.io/binaryen

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