Specifications - WebAssembly

Overview Getting Started Specs Docs Feature Status Community News Specifications WebAssembly Specification (Wasm 3.0): defines the semantics of WebAssembly modules independent from a concrete embedding. The WebAssembly core is specified in a single document.\ Older versions: WebAssembly Core Specification — W3C Candidate Recommendation Draft, 16 June 2025 (Wasm 2.0) WebAssembly Core Specification — W3C Recommendation, 5 December 2019 (Wasm 1.0) Embedding interfaces: JavaScript API: defines JavaScript classes and objects for accessing WebAssembly from within JavaScript, including methods for validation, compilation, instantiation, and classes for representing and manipulating imports and exports as JavaScript objects. Web API: defines extensions to the JavaScript API made available specifically in web browsers, in particular, an interface for streaming compilation and instantiation from origin-bound Response types. WASI API: defines a modular system interface to run WebAssembly outside the web, providing access to things like files, network connections, clocks, and random numbers. Tool conventions: repository describing non-standard conventions useful for coordinating interoperability between tools working with WebAssembly. This includes conventions for linking schemes, debugging information, language ABIs and more. Original design documents: documents describing the design, goals and high-level overview of WebAssembly. Some of these documents are outdated by now.