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On the recordRead 30 Sep 202621 facts
Mock Service Worker
On the record
- Additional integrations
- The MSW organization lists extensions for Playwright, Storybook, Cloudflare workerd, and SvelteKit.github.com · read 30 Sep 2026
- Browser integration
- In browsers, MSW uses the Service Worker API to intercept requests at the network level.mswjs.io · read 30 Sep 2026
- Browser limitation
- Because browser interception relies on the Service Worker API, browser-specific limitations apply; the docs also state that Firefox does not notify the worker about page XMLHttpRequest requests.mswjs.io · read 30 Sep 2026
- Client compatibility
- The documentation names native fetch and third-party clients including Axios, React Query, and Apollo as supported request clients.mswjs.io · read 30 Sep 2026
- Learning resources
- The documentation says its official Egghead courses require a paid subscription and help support the project.mswjs.io · read 30 Sep 2026
- Limitations
- MSW's GraphQL documentation says it supports queries and mutations, while subscriptions are described as coming in the future.mswjs.io · read 30 Sep 2026
- Network APIs
- MSW supports mocking REST, GraphQL, Server-Sent Events, and WebSocket APIs.mswjs.io · read 30 Sep 2026
- Network standards
- MSW uses the Fetch API to handle intercepted requests and construct mocked responses, including requests made with other clients.mswjs.io · read 30 Sep 2026
- Node integration
- In Node.js, MSW intercepts raw socket connections before they reach the network code written in C.mswjs.io · read 30 Sep 2026
- Node.js integration
- In Node.js, MSW provides setupServer for enabling API mocking in an application process or test runner.mswjs.io · read 30 Sep 2026
- Node.js limitation
- MSW cannot intercept requests made directly through net.connect() or net.createConnection(), which some libraries use.mswjs.io · read 30 Sep 2026
- Open source
- The project describes MSW as open-source and free to try.mswjs.io · read 30 Sep 2026
- Paid learning
- The documentation says its official Egghead courses require a paid subscription.mswjs.io · read 30 Sep 2026
- Protocols
- MSW supports mocking HTTP, GraphQL, Server-Sent Events, and WebSocket APIs.mswjs.io · read 30 Sep 2026
- Purpose
- Mock Service Worker (MSW) is an API mocking library for browser and Node.js that intercepts outgoing requests so developers can observe and respond with mocked responses.mswjs.io · read 30 Sep 2026
- Request clients
- MSW works with native fetch and third-party clients such as Axios, React Query, and Apollo.mswjs.io · read 30 Sep 2026
- Reusable mocks
- The same mock handlers can be reused for development, integration and end-to-end testing, Storybook, and live demos.mswjs.io · read 30 Sep 2026
- Shared mocks
- The same client-agnostic mocks can be reused across frameworks, tools, and environments, including development, integration and end-to-end testing, Storybook, and live demos.mswjs.io · read 30 Sep 2026
