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README.md

Mock Service Worker is an API mocking library for browser and Node.js that uses a Service Worker to intercept requests that actually happened. This means no request client stubs and unmatched resilience when it comes to request integrity, as your app now performs requests the same way it does in production.

Ecosystem

We favor composition in both how we write our code and how we distribute it. That's why instead of building a single monolithic package that's responsible for too many things, we distribute thecore module with the essentials that everybody could use, and provide a set of standaloneextensions that enable specific workflows and push the developer experience even further.

Native extensions

Package	Description
`@msw/data`	Model and query your mock data (fixtures).
`@mswjs/source`	Generate request handlers from various sources (HAR files, OpenAPI documents).
`@mswjs/http-middleware`	Spawn an HTTP server from your request handlers.

Third-party extensions

Package	Description
`@msw/playwright`	Official Playwright integration.
`msw-storybook-addon`	Official Storybook add-on.

Support us!

This project is the result of hundreds of hours of work that our contributors spend so that you could enjoy the best API mocking experience there is to offer. If you'd like us to bring new features and mitigate issues more effectively, consider supporting us.

👉Support Mock Service Worker via GitHub Sponsors

By becoming a baker you help us ensure a bright future for the project. We value and treasure every contribution, big or small. Thank you.

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mswmswPublic
Industry standard API mocking for JavaScript.
TypeScript 17.3k 563
examplesexamplesPublic
Examples of Mock Service Worker usage with various frameworks and libraries.
712 210
datadataPublic
Data querying library for testing JavaScript applications.
TypeScript 951 61
interceptorsinterceptorsPublic
Low-level network interception library.
TypeScript 617 148
msw-storybook-addonmsw-storybook-addonPublic
Mock API requests in Storybook with Mock Service Worker.
TypeScript 469 43
http-middlewarehttp-middlewarePublic
Spawn an HTTP server from your request handlers or apply them to an existing server using a middleware.
TypeScript 121 12

Showing 10 of 23 repositories

mswjs.io Public
Official website and documentation for the Mock Service Worker library.
mswjs/mswjs.io’s past year of commit activity
TypeScript 171 216 13 (1 issue needs help) 16 UpdatedNov 5, 2025
msw Public
Industry standard API mocking for JavaScript.
mswjs/msw’s past year of commit activity
TypeScript 17,274MIT 563 51 (5 issues need help) 10 UpdatedNov 5, 2025
interceptors Public
Low-level network interception library.
mswjs/interceptors’s past year of commit activity
TypeScript 617MIT 148 23 (1 issue needs help) 13 UpdatedOct 19, 2025
data Public
Data querying library for testing JavaScript applications.
mswjs/data’s past year of commit activity
TypeScript 951MIT 61 2 3 UpdatedOct 16, 2025
msw-storybook-addon Public
Mock API requests in Storybook with Mock Service Worker.
mswjs/msw-storybook-addon’s past year of commit activity
TypeScript 469MIT 43 18 (1 issue needs help) 2 UpdatedOct 10, 2025
source Public
Generate MSW request handlers from various sources (HAR files, OpenAPI documents, etc).
mswjs/source’s past year of commit activity
TypeScript 196MIT 10 10 1 UpdatedOct 9, 2025
codemods Public
Automate repetitive and painful MSW migrations & breaking changes.
mswjs/codemods’s past year of commit activity
TypeScript 5MIT0 0 0 UpdatedOct 2, 2025
.github Public
Mock Service Worker organization GitHub files.
mswjs/.github’s past year of commit activity
00 0 0 UpdatedSep 29, 2025
examples Public
Examples of Mock Service Worker usage with various frameworks and libraries.
mswjs/examples’s past year of commit activity
712 210 11 (1 issue needs help) 10 UpdatedSep 16, 2025
jest-fixed-jsdom Public
A superset of the JSDOM environment for Jest that respects Node.js globals.
mswjs/jest-fixed-jsdom’s past year of commit activity
JavaScript 93 8 13 0 UpdatedAug 30, 2025