wasm3  0.5.0
About: Wasm3 is a fast WebAssembly interpreter.
  Fossies Dox: wasm3-0.5.0.tar.gz  ("unofficial" and yet experimental doxygen-generated source code documentation)  

wasm3 Documentation

Some Fossies usage hints in advance:

  1. To see the Doxygen generated documentation please click on one of the items in the steelblue colored "quick index" bar above or use the side panel at the left which displays a hierarchical tree-like index structure and is adjustable in width.
  2. If you want to search for something by keyword rather than browse for it you can use the client side search facility (using Javascript and DHTML) that provides live searching, i.e. the search results are presented and adapted as you type in the Search input field at the top right.
  3. Doxygen doesn't incorporate all member files but just a definable subset (basically the main project source code files that are written in a supported language). So to search and browse all member files you may visit the Fossies wasm3-0.5.0.tar.gz contents page and use the Fossies standard member browsing features (also with source code highlighting and additionally with optional code folding).


WAPM GitHub issues Tests status Fuzzing Status GitHub license

The fastest WebAssembly interpreter, and the most universal runtime.
Based on CoreMark 1.0 and independent benchmarks. Your mileage may vary.

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Getting Started

Here's a small getting started guide. Click here to start:



Please follow the installation instructions.

Wasm3 can also be used as a library for:

Python3 Rust C/C++ GoLang  Zig
Swift .Net Arduino, PlatformIO, Particle


wasm3 passes the WebAssembly spec testsuite and is able to run many WASI apps.

Minimum useful system requirements: ~64Kb for code and ~10Kb RAM

wasm3 runs on a wide range of architectures (x86, x86_64, ARM, RISC-V, PowerPC, MIPS, Xtensa, ARC32, ...) and platforms:

  • Linux, Windows, OS X, FreeBSD, Android, iOS
  • OpenWrt, Yocto, Buildroot (routers, modems, etc.)
  • Raspberry Pi, Orange Pi and other SBCs
  • MCUs: Arduino, ESP8266, ESP32, Particle, ... see full list
  • Browsers. Yes, using WebAssembly itself!
  • wasm3 can execute wasm3 (self-hosting)

Advanced features and post-mvp proposals support

☑ Sign-extension operators
☑ Non-trapping float-to-int conversions
☑ Import/Export of Mutable Globals
☑ Structured execution tracing
☑ Big-Endian systems support
☑ Self-hosting
☑ Gas metering
☑ Multi-value
☐ Reference types
☐ Bulk memory operations
☐ Tail call optimization


Why use a "slow interpreter" versus a "fast JIT"?

In many situations, speed is not the main concern. Runtime executable size, memory usage, startup latency can be improved with the interpreter approach. Portability and security are much easier to achieve and maintain. Additionally, development impedance is much lower. A simple library like Wasm3 is easy to compile and integrate into an existing project. (Wasm3 builds in a just few seconds). Finally, on some platforms (i.e. iOS and WebAssembly itself) you can't generate executable code pages in runtime, so JIT is unavailable.

Why would you want to run WASM on embedded devices?

Wasm3 started as a research project and remains so by many means. Evaluating the engine in different environments is part of the research. Given that we have Lua, JS, Python, Lisp, ... running on MCUs, WebAssembly is actually a promising alternative. It provides toolchain decoupling as well as a completely sandboxed, well-defined, predictable environment. Among practical use cases we can list edge computing, scripting, running IoT rules, smart contracts, etc.

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Further Resources

Installation instructions
Build and Development instructions
Supported Hardware
Testing & Fuzzing
Interpreter Architecture
Awesome WebAssembly Tools


This project is released under The MIT License (MIT)