Component Model

aid: component-model
url: https://raw.githubusercontent.com/api-evangelist/component-model/refs/heads/main/apis.yml
name: Component Model
kind: standard
description: The WebAssembly Component Model is a broad-reaching architecture for building interoperable WebAssembly libraries,
  applications, and environments. It defines components as portable, sandboxed units of code that can compose with each other
  across language and runtime boundaries. The model introduces interfaces, worlds, and the WebAssembly Interface Type (WIT)
  language, along with a canonical ABI, binary and text formats, and a concurrency model. The Component Model underpins the
  WebAssembly System Interface (WASI) Preview 2 and is the foundation for portable Wasm on browsers, servers, edge, and embedded
  environments.
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
tags:
- ABI
- Bytecode Alliance
- Component
- Interface
- Modular
- Specification
- WASI
- WebAssembly
- WIT
- World
created: '2025-01-01'
modified: '2026-04-28'
specificationVersion: '0.19'
apis:
- aid: component-model:specification
  name: WebAssembly Component Model Specification
  description: The Component Model specification repository under the W3C WebAssembly Community Group. Contains design documents,
    the formal specification drafts, the WIT grammar, the canonical ABI, and the binary and text formats that define a WebAssembly
    component.
  humanURL: https://github.com/WebAssembly/component-model
  baseURL: https://github.com/WebAssembly
  tags:
  - Specification
  - W3C
  - WebAssembly
  properties:
  - type: GitHubRepository
    url: https://github.com/WebAssembly/component-model
  - type: Documentation
    url: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Explainer.md
  - type: Specification
    url: https://github.com/WebAssembly/component-model/tree/main/design/mvp
  - type: Reference
    url: https://github.com/WebAssembly/component-model/blob/main/design/mvp/CanonicalABI.md
  - type: Reference
    url: https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md
  x-features:
  - Defines components, interfaces, and worlds
  - Introduces WIT, the WebAssembly Interface Type language
  - Specifies a canonical ABI between components and host
  - Provides binary and text formats for components
  - Foundation for WASI Preview 2 system interfaces
  x-useCases:
  - Tracking the evolving Component Model standard
  - Implementing language toolchains targeting components
  - Implementing runtimes that load and link components
- aid: component-model:wit
  name: WebAssembly Interface Type (WIT)
  description: WIT is the interface definition language for the Component Model. WIT describes the imports and exports of
    a component using interfaces and worlds. WIT is consumed by language toolchains to generate bindings and by runtimes to
    validate and link components at load time.
  humanURL: https://component-model.bytecodealliance.org/design/wit.html
  baseURL: https://component-model.bytecodealliance.org
  tags:
  - Bindings
  - IDL
  - Interface
  - WIT
  properties:
  - type: Documentation
    url: https://component-model.bytecodealliance.org/design/wit.html
  - type: Specification
    url: https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md
  - type: Reference
    url: https://github.com/bytecodealliance/wit-bindgen
  x-features:
  - Declarative IDL for components
  - Records, variants, enums, flags, options, results
  - Resources with methods for borrowed and owned references
  - Interfaces compose into worlds
  x-useCases:
  - Authoring portable component interfaces
  - Generating language bindings via wit-bindgen
  - Defining stable contracts between platform and components
- aid: component-model:wasi-preview-2
  name: WebAssembly System Interface Preview 2
  description: WASI Preview 2 is the first WASI release built on the Component Model. It defines a set of interfaces such
    as wasi:filesystem, wasi:io, wasi:http, wasi:cli, and wasi:sockets that components can import to interact with the host
    system in a portable, capability-based way.
  humanURL: https://wasi.dev/
  baseURL: https://wasi.dev
  tags:
  - System Interface
  - WASI
  - Capabilities
  properties:
  - type: Documentation
    url: https://wasi.dev/
  - type: GitHubOrganization
    url: https://github.com/WebAssembly/WASI
  - type: Reference
    url: https://github.com/WebAssembly/wasi-http
  - type: Reference
    url: https://github.com/WebAssembly/wasi-filesystem
  x-features:
  - Capability-based system access
  - Defined as a collection of WIT worlds
  - wasi:http provides a portable HTTP server interface
  - Worlds for CLI, HTTP proxy, and embedder customization
  x-useCases:
  - Building portable WebAssembly server functions
  - Running components in Wasmtime, Jco, WasmEdge, and Spin
  - Implementing capability-secure host bindings
- aid: component-model:bytecode-alliance-implementations
  name: Component Model Implementations
  description: A landscape of toolchains and runtimes that implement the Component Model, including Wasmtime, Jco, wit-bindgen
    language bindings, cargo-component for Rust, ComponentizeJS, and Spin for serverless Wasm. These implementations are largely
    stewarded by the Bytecode Alliance.
  humanURL: https://bytecodealliance.org/
  baseURL: https://bytecodealliance.org
  tags:
  - Bytecode Alliance
  - Implementations
  - Runtimes
  - Toolchains
  properties:
  - type: Reference
    url: https://github.com/bytecodealliance/wasmtime
  - type: Reference
    url: https://github.com/bytecodealliance/wit-bindgen
  - type: Reference
    url: https://github.com/bytecodealliance/cargo-component
  - type: Reference
    url: https://github.com/bytecodealliance/jco
  - type: Reference
    url: https://github.com/bytecodealliance/ComponentizeJS
  - type: Reference
    url: https://github.com/fermyon/spin
  x-features:
  - Wasmtime native runtime with component support
  - Jco JavaScript host and tooling
  - cargo-component for Rust component projects
  - wit-bindgen for cross-language bindings
  x-useCases:
  - Running components on the server, edge, or in browsers
  - Generating language bindings from WIT
  - Building serverless Wasm functions on Spin
common:
- type: Website
  url: https://component-model.bytecodealliance.org/
- type: Documentation
  url: https://component-model.bytecodealliance.org/design/
- type: GitHubRepository
  url: https://github.com/WebAssembly/component-model
- type: GitHubOrganization
  url: https://github.com/WebAssembly
- type: Reference
  url: https://wasi.dev/
- type: Reference
  url: https://bytecodealliance.org/
- type: Working Group
  url: https://www.w3.org/community/webassembly/
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com