Mock API

A simulated API endpoint that returns predefined responses for testing and development.

A Mock API is a fake API endpoint that simulates the behavior of a real API. It returns predefined or dynamically generated responses, allowing developers to work without depending on actual backend services.

Mock API vs Real API

Aspect	Mock API	Real API
Data	Predefined/Generated	Live database
Availability	Always available	May have downtime
Speed	Instant responses	Network latency
Cost	Free	May have usage fees

Common Use Cases

Frontend Development: Build UI before backend is ready
Unit Testing: Isolate components from external dependencies
Demo & Prototyping: Show functionality without real data
CI/CD Pipelines: Run tests without external services

Creating Mock APIs

JSON Files: Simple static responses
Mock Servers: Tools like JSON Server, Mockoon
Cloud Services: Mockable.io, Beeceptor, MockAPI
Code-Based: MSW, Nock, WireMock

Code Examples

JSON Server db.json

{
  "users": [
    { "id": 1, "name": "John Doe", "email": "john@example.com" },
    { "id": 2, "name": "Jane Smith", "email": "jane@example.com" }
  ],
  "posts": [
    { "id": 1, "title": "Hello World", "userId": 1 }
  ]
}

Related Terms

REST API

An architectural style for building web APIs using HTTP methods and stateless communication.

OpenAPI Specification

A standard format for describing REST APIs, enabling documentation and code generation.

Latency

The time delay between a request being sent and a response being received.

HTTP Status Codes

Standard response codes that indicate the result of an HTTP request.