Generate mock JSON API responses from schema templates and presets
The API Response Simulator generates mock JSON API responses from preset templates (User, Product, Order, E-Commerce Cart, Blog Posts, Support Tickets) or custom schemas. Choose an HTTP status code and simulate network latency to see how your frontend handles every scenario — all locally in your browser.
Zero server lag. All generation runs locally on your device for maximum speed.
Your data never leaves your device. No uploads, no servers, no tracking.
As we move into 2026, the complexity of frontend applications has increased exponentially. Developers often find themselves in a "chicken and egg" situation where the frontend needs to be built before the backend API is ready. This is where an API Response Simulator becomes indispensable. By using mock data that mimics the structure and behavior of your eventual production API, you can build, test, and debug your UI in total isolation.
Our simulator goes beyond simple JSON generation by supporting full HTTP status simulation — generate a 500 Server Error response and observe how your error boundary renders, or throw a 401 Unauthorized and verify your auth redirect logic. Combined with the built-in Network Latency Slider (0→5000 ms), you can also test loading skeletons, skeleton screens, and optimistic UI patterns without ever leaving your browser.
The Local-First philosophy of AllOmnitools means every feature runs entirely on your machine. No cloud account, no rate limits, no data leaving your device. Build complex schemas locally, download them as mock-data.json, and drop them straight into your test suite.
Yes. Select any HTTP status code from the dropdown — 400 Bad Request, 401 Unauthorized, 404 Not Found, or 500 Server Error — and the generated response will include a matching error body so you can test failure states in your frontend.
Yes. Use the Simulated Delay slider (0→5000 ms) before clicking Generate. The UI will show a loading spinner for the chosen duration so you can evaluate skeletons, spinners, and timeout behavior under realistic network conditions.
User, Product, Order, E-Commerce Cart, Blog Posts / Comments, and Support Tickets presets are included — each with realistic field names and data types ready to generate.
Yes. Select "Custom Schema" and define your fields as a JSON array with name and type properties. Supported types include string, number, boolean, date, UUID, phone, and image URL.
You can generate between 1 and 100 records per request. All generation happens locally in your browser using high-performance JavaScript, ensuring instant results regardless of your internet speed.
No. At AllOmnitools, we prioritize your privacy. Everything happens client-side. Your custom schemas and the generated data never leave your device, making it safe for use with proprietary project structures.
While this tool is primarily for manual development and prototyping, you can copy the generated JSON or download it as mock-data.json and use it as a static fixture in your unit tests or integration test suites (like Jest or Cypress).