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Apr 29, 2015

WebAssembly Design

This repository contains documents describing the design and high-level overview of WebAssembly.

The documents and discussions in this repository are part of the WebAssembly Community Group.


WebAssembly or wasm is a new, portable, size- and load-time-efficient format suitable for compilation to the web.

WebAssembly is currently being designed as an open standard by a W3C Community Group that includes representatives from all major browsers. Expect the contents of this repository to be in flux: everything is still under discussion.

  • WebAssembly is efficient and fast: Wasm bytecode is designed to be encoded in a size- and load-time-efficient binary format. WebAssembly aims to execute at native speed by taking advantage of common hardware capabilities available on a wide range of platforms.

  • WebAssembly is safe: WebAssembly describes a memory-safe, sandboxed execution environment that may even be implemented inside existing JavaScript virtual machines. When embedded in the web, WebAssembly will enforce the same-origin and permissions security policies of the browser.

  • WebAssembly is open and debuggable: WebAssembly is designed to be pretty-printed in a textual format for debugging, testing, experimenting, optimizing, learning, teaching, and writing programs by hand. The textual format will be used when viewing the source of wasm modules on the web.

  • WebAssembly is part of the open web platform: WebAssembly is designed to maintain the versionless, feature-tested, and backwards-compatible nature of the web. WebAssembly modules will be able to call into and out of the JavaScript context and access browser functionality through the same Web APIs accessible from JavaScript. WebAssembly also supports non-web embeddings.

More Information

Resource Repository Location
High Level Goals design/
Frequently Asked Questions design/
Language Specification spec/

Design Process & Contributing

The WebAssembly specification is being developed in the spec repository. For now, high-level design discussions should continue to be held in the design repository, via issues and pull requests, so that the specification work can remain focused.

We've mapped out features we expect to ship:

  1. An initial Minimum Viable Product (MVP) release;
  2. And soon after in future versions.

Join us:

When contributing, please follow our Code of Ethics and Professional Conduct.