Create realistic API endpoints with custom responses, status codes, and delays. Perfect for frontend development, demos, and integration testing.
Note
This tool helps you design and document mock APIs. To expose them on the internet you can copy the generated configuration into tools like json-server, Express, or online mock API platforms.
curl -X POST -H "Content-Type: application/json" -d '{"token":"ey.fake.jwt.token","user":{"id":"user_123","name":"Jane Doe","email":"jane@example.com","roles":["admin","editor"]}}' "https://mock-api.sourcecodestack.com/auth/login"// Click "Test Endpoint" or "Webhook" to simulate a response
Mock API Server is a free, browser-based tool that lets you create simulated API endpoints for frontend development and testing — without needing a real backend server. Define custom routes with specific HTTP methods, status codes, response bodies, and headers, then use them to test your application's behavior against different API scenarios. It is ideal for prototyping, testing error handling, simulating slow responses, and developing frontend features before the backend is ready.
Yes. The Mock API Server is designed exactly for this purpose. Create endpoints that mirror your planned API structure, configure the responses, and point your frontend to the mock URLs during development.
When creating or editing an endpoint, set the status code to any error code you want to test — such as 400 (Bad Request), 403 (Forbidden), 404 (Not Found), or 500 (Internal Server Error). You can also customize the error response body to match realistic error formats.
Yes. Each endpoint supports configurable response delays in milliseconds. This is useful for testing loading states, timeout handling, and how your UI behaves under slow network conditions.
Mock configurations persist in your browser session. For long-term storage, you can export your endpoint definitions and re-import them later. Your data stays local and is never sent to any server.
This tool complements them. It is lighter and requires zero setup — just open the page and start mocking. For complex scenarios like chained responses, conditional logic, or team collaboration, dedicated tools like Postman or Mockoon offer additional features.
A mock API server is a simulated backend that responds to HTTP requests with predefined data, without real business logic, database, or infrastructure. It solves one of the most common friction points in development: frontend and backend teams working in parallel on the same feature. When the frontend team needs an endpoint the backend team has not built yet, work stalls. A mock API breaks this dependency — frontend developers build against a working simulation immediately, while backend developers implement the real thing in parallel.
Mock, stub, and fake are often confused. A stub returns a hardcoded response regardless of input. A mock verifies it was called in specific ways and simulates scenarios based on input. A fake is a working implementation with simplified behavior (like an in-memory database). In everyday usage, "mock API" typically means stub-level behavior: define an endpoint, define its response, done.
Modern mock servers go well beyond simple stubbing. They support configurable HTTP status codes to simulate errors (404, 500, 429), artificial response delays to test loading state UI, request validation to ensure callers send the expected shape, and response templates with dynamic data generation. This makes them invaluable for building robust test suites covering edge cases that would be difficult or destructive to trigger against a real backend — like testing what happens when a payment service returns 503.
A mock API is a simulated web service that accepts HTTP requests and returns predefined responses, mimicking a real API without real infrastructure. You define the endpoint path, HTTP method, status code, and response body — typically a JSON payload. Your application hits that URL and receives a realistic response instantly, allowing development to proceed without a real backend.
The real API executes actual business logic — queries a database, applies rules, sends emails, charges credit cards. A mock only returns what you configured; no writes persist, no logic executes. The value of a mock is behavioral consistency for the contract (URL, method, headers, response shape), not functional correctness. Once the real API is built, integration testing against it is essential before shipping.
Configure a mock endpoint to return the desired HTTP error status — 404 for not found, 500 for server error, 429 for rate limiting, 503 for service unavailable — with an appropriate error response body. Advanced mock servers let you configure conditional responses: return 200 for valid requests and 404 for unrecognized IDs. Adding a simulated delay lets you test timeout handling and loading spinners realistically.
No — mock APIs do not persist data, enforce business rules, validate security, or integrate with real systems. Users interacting with a mock-backed production app would lose all data. The only exception: graceful degradation patterns that fall back to canned responses when a downstream service is unavailable — but this is handled intentionally in application code, not by routing real traffic to a mock server.
API contract testing verifies that a consumer (frontend) and a provider (backend) agree on the API shape — exact URLs, methods, request schemas, and response schemas. Tools like Pact formalize this contract: the consumer generates a contract file from mock interactions, and the provider runs tests to verify it satisfies every contract. This catches breaking changes — like a backend developer renaming a JSON field — before they reach production.
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