Mock Service Worker

aid: mock-service-worker
name: Mock Service Worker
description: >-
  Mock Service Worker (MSW) is an industry-standard, open-source API mocking
  library for the browser and Node.js. MSW intercepts outgoing requests at the
  network level using Service Workers in browsers and a request interception
  algorithm in Node.js, allowing developers to write client-agnostic mocks for
  HTTP, GraphQL, WebSocket, and Server-Sent Events and reuse them across any
  framework, tool, or environment for development, testing, and debugging.
type: Index
image: https://kinlane-images.s3.amazonaws.com/shared/apis-json/apis-json-logo.jpg
url: >-
  https://raw.githubusercontent.com/api-evangelist/mock-service-worker/refs/heads/main/apis.yml
tags:
- API Mocking
- GraphQL
- HTTP
- Mock Server
- Mocking
- Service Worker
- Testing
- WebSocket
access: 3rd-Party
position: Consumer
created: '2025-01-08'
modified: '2026-04-28'
specificationVersion: '0.20'
apis:
- aid: mock-service-worker:msw
  name: Mock Service Worker
  description: >-
    Mock Service Worker (MSW) is an open-source library for mocking REST,
    GraphQL, WebSocket, and Server-Sent Events APIs at the network level. It
    provides setupWorker for browser environments and setupServer for Node.js,
    with handlers (http, graphql, ws, sse) that allow developers to declare
    mocked responses without modifying application code.
  image: >-
    https://mswjs.io/static/logos/msw-logo.svg
  humanURL: https://mswjs.io/
  baseURL: https://mswjs.io/
  tags:
  - API Mocking
  - GraphQL
  - HTTP
  - Mocking
  - Service Worker
  - Testing
  - WebSocket
  properties:
  - type: Documentation
    url: https://mswjs.io/docs/
  - type: GettingStarted
    url: https://mswjs.io/docs/quick-start
  - type: HTTP Handler
    url: https://mswjs.io/docs/network-behavior/rest
  - type: GraphQL Handler
    url: https://mswjs.io/docs/network-behavior/graphql
  - type: WebSocket Handler
    url: https://mswjs.io/docs/network-behavior/websocket
  - type: GitHub
    url: https://github.com/mswjs/msw
  - type: Examples
    url: https://github.com/mswjs/examples
  - type: NPM
    url: https://www.npmjs.com/package/msw
  - type: License
    url: https://github.com/mswjs/msw/blob/main/LICENSE.md
  - url: graphql/mock-service-worker-graphql.md
    type: GraphQL
  contact:
  - FN: MSW Maintainers
    url: https://github.com/mswjs/msw
common:
- type: Website
  url: https://mswjs.io/
- type: Documentation
  url: https://mswjs.io/docs/
- type: GettingStarted
  url: https://mswjs.io/docs/quick-start
- type: GitHub
  url: https://github.com/mswjs/msw
- type: Examples
  url: https://github.com/mswjs/examples
- type: NPM
  url: https://www.npmjs.com/package/msw
- type: Discord
  url: https://kettanaito.com/discord
- type: Sponsor
  url: https://github.com/sponsors/mswjs
- type: OpenCollective
  url: https://opencollective.com/mswjs
- type: License
  url: https://github.com/mswjs/msw/blob/main/LICENSE.md
- type: JSONLD
  url: json-ld/mock-service-worker-context.jsonld
- type: JSONSchema
  url: json-schema/mock-service-worker-handler-schema.json
- type: Integrations
  url: https://mswjs.io/ecosystem
integrations:
- name: Data
- name: Source
maintainers:
- FN: Kin Lane
  email: kin@apievangelist.com
  url: https://apievangelist.com