Mock API Builder
Design mock REST API endpoints with custom responses and config
Design mock REST API endpoints with custom JSON responses, status codes, and headers — perfect for frontend development when the real backend is not ready yet.
Common HTTP status codes
| Code | Name | When to use |
|---|---|---|
| 200 | OK | Successful GET/PATCH/PUT |
| 201 | Created | Successful POST that created a resource |
| 204 | No Content | Successful DELETE with no body |
| 400 | Bad Request | Client sent invalid data |
| 401 | Unauthorized | Missing or invalid authentication |
| 403 | Forbidden | Authenticated but not allowed |
| 404 | Not Found | Resource does not exist |
| 409 | Conflict | Resource state conflicts (e.g. duplicate) |
| 422 | Unprocessable Entity | Validation errors |
| 500 | Server Error | Something broke server-side |
Why use a mock API?
- Start frontend work before the backend is ready.
- Test edge cases (500 errors, slow responses) that are hard to reproduce in real APIs.
- Build prototypes and demos without spinning up infrastructure.
- Give designers and PMs clickable demos.
Frequently asked questions
What is a mock API?
An API that returns predefined responses instead of real data. Used in development and testing.
Can I use it from my app?
Yes — point your fetch/axios calls at the mock endpoint URL.
Can I add dynamic responses?
Yes — use templates to return different responses based on request params or body.
Can I simulate network latency?
Yes, set a delay per endpoint to test loading states and timeouts.