API Mock Server Generator

Instantly generate mock API server code for Express, Next.js, or MSW from a JSON payload. Runs entirely in your browser, free forever.

100% private — this runs entirely in your browser and nothing is uploaded.

Mock Server Config

Target Framework

HTTP Method

Endpoint Path (e.g., /api/users/:id)

Simulate 1s LatencySimulate Errors (30% 500s)

JSON Response Payload

Generated Server Code

const express = require('express');
const app = express();
const port = 3000;

app.use(express.json()); // For parsing application/json

// Enable CORS
app.use((req, res, next) => {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  res.header("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, PATCH, OPTIONS");
  next();
});

// Mock Data
const mockData = [
  {
    "id": 1,
    "name": "Alice"
  },
  {
    "id": 2,
    "name": "Bob"
  }
];

// Endpoint
app.get('/api/users', (req, res) => {
  res.status(200).json(mockData);
});

app.listen(port, () => {
  console.log(`Mock API server running at http://localhost:${port}`);
});

When building frontend applications, waiting for backend developers to finish an API endpoint can slow down development.

With the API Mock Server Generator, you can simply paste the expected JSON response, choose your framework (Express.js, Next.js, or MSW), and instantly get a working mock server implementation. Copy the generated code into your project to start fetching data immediately!

Related Tools

API Request Builder

Build API requests with an intuitive UI and instantly generate code snippets for cURL, Fetch, and Axios.

JSON Formatter Online — Beautify & Pretty Print JSON

Free online JSON formatter and beautifier. Instantly pretty print, validate, and format JSON with 2 or 4-space indentation. Runs 100% in your browser.