MSW vs Nock

Choosing between the two most popular HTTP mocking libraries

When you need to mock HTTP requests in JavaScript or TypeScript tests, two tools dominate:MSW (Mock Service Worker) and Nock. Both are mature, well-maintained, and widely adopted, but they take fundamentally different approaches to interception.

At a Glance

MSW

  • ✅ Works in browser and Node.js
  • ✅ Network-level interception (Service Worker)
  • ✅ Same API everywhere
  • ✅ Great for full-stack apps
  • ❌ Slightly more setup
  • ❌ No built-in recording

Nock

  • ✅ Dead simple API
  • ✅ Built-in record/replay
  • ✅ Powerful request matching
  • ✅ Battle-tested since 2011
  • ❌ Node.js only
  • ❌ Patches HTTP module

Which Should You Choose?

Choose MSW if...

  • You're building a React, Vue, or Angular app with browser tests
  • You want the same mocking code in both browser and Node.js
  • You prefer network-level interception over module patching
  • You want to use mocks in development, not just tests

Best for: Modern web applications with component + integration tests

Choose Nock if...

  • You're only testing Node.js code (backend services, APIs)
  • You want the absolute simplest API possible
  • You need to record real API calls and replay them
  • You don't need browser support

Best for: Backend Node.js services and APIs

Side-by-Side Code Example

MSW

import { http, HttpResponse } from 'msw'
import { setupServer } from 'msw/node'

const server = setupServer(
  http.get('/api/user', () => {
    return HttpResponse.json({
      id: 1,
      name: 'John Doe'
    })
  })
)

beforeAll(() => server.listen())
afterEach(() => server.resetHandlers())
afterAll(() => server.close())

Nock

import nock from 'nock'

nock('https://api.example.com')
  .get('/api/user')
  .reply(200, {
    id: 1,
    name: 'John Doe'
  })

// That's it! Nock intercepts 
// matching requests automatically

Detailed Comparison

FeatureMSWNock
Browser Support✅ Yes❌ No
Node.js Support✅ Yes✅ Yes
Interception MethodService Worker / Native modulesPatches Node.js HTTP module
Record/Replay❌ No✅ Yes
TypeScript Support✅ Native✅ Yes (types included)
Learning CurveMediumLow
GitHub Stars16k+12k+
First Released20182011

Also Consider: Polly.js

If you need record/replay functionality with browser support, check out Polly.js. Built by Netflix, it works in both environments and specializes in recording real API traffic. It's more complex to set up than MSW or Nock, but fills a unique niche.

See Full Three-Way Comparison →