API mocking tool for frontend development

For quickly mocking a REST API during frontend development, I'd start with Mock Service Worker (MSW) if you want realistic API behavior without building a separate backend. If you want to create endpoints visually and get a working mock API in minutes, a hosted tool like Mockoon or Beeceptor may be a better fit.

The best choice depends on whether you want to mock requests inside your frontend app, run a local mock server, or share an API with your team.

My top 3 picks

1. Mock Service Worker (MSW)

(Best for frontend developers)

Intercepts requests in the browser or Node.js, letting you define mock responses in code while your frontend uses its normal fetch or API client. Great for React, Vue, and automated tests.

Best when: you want mocks version-controlled alongside your app and easy to switch off later.

Website:mswjs.io

2. Mockoon

(Best local mock server)

A desktop app with a visual interface for creating REST endpoints, defining JSON responses, adding rules, and simulating realistic API behavior. It is free and open source, with no account required for the core app.mockoon.com+1

Best when: you want a real local API URL such as http://localhost:3000/api/users, without writing a backend.

Website:mockoon.com

3. Beeceptor

(Best for zero-setup sharing)

Creates hosted mock endpoints you can call from your frontend. Configure response bodies, HTTP status codes, request-matching rules, and latency in its dashboard. It can also generate a mock API from an OpenAPI specification.beeceptor.com+1

Best when: you want a shareable API URL for teammates, demos, or a frontend that needs to run on multiple machines.

Website:beeceptor.com

Which one should you choose?

Quick example: mocking an endpoint with MSW

Install it:

npm install msw

Define a mock GET /api/users endpoint:

import { http, HttpResponse } from 'msw';

export const handlers = [
  http.get('/api/users', () => {
    return HttpResponse.json([
      { id: 1, name: 'Alice' },
      { id: 2, name: 'Bob' },
    ]);
  }),
];

Once MSW is configured in your development environment, your frontend can call /api/users normally and receive the mock JSON response. You don't need to change your application's request code to accommodate the mock.

My verdict: Start with MSW if you're building the frontend in code. Choose Mockoon if you specifically need a standalone REST server. Choose Beeceptor if you want the least setup and a URL that other developers can access.

One question that would help me narrow it down: Are you using React/Next.js, Vue, Angular, or something else? I can recommend the simplest setup for your stack.