REST API Mock Generator

A REST API mock is a fake JSON response that mimics what a real API endpoint would return. Mocks are essential during frontend development so you can build and test UI before the backend is ready, in automated tests where you want deterministic, isolated responses, and in demos where you cannot expose real data. Generating realistic mock data instantly removes the setup overhead of writing fixture files by hand.

The generator includes built-in templates for eight common REST resource types: User, Product, Order, Article/Post, Comment, Company, Invoice, and Event. Each template contains a realistic set of fields you can toggle on or off. You can also choose the Custom mode and paste your own JSON schema — the generator will create multiple records from your template.

When the response wrapper is enabled, the output is structured as { "data": [...], "meta": { "total": N, "page": 1, "limit": 20 } } — a common envelope pattern used by REST APIs to carry both the resource array and pagination metadata in a single response. When disabled, the output is a plain JSON array. The wrapper is automatically disabled for error status codes.

When you select an HTTP error status (400, 401, 403, 404, 422, or 500), the generator switches to an error response format with a structured { error: { code, message } } body appropriate for that status. For example, 400 Bad Request includes a field-level validation detail, 422 Unprocessable Entity includes a per-field errors map, and 401/403 include authentication/authorization messages. This lets you test how your frontend handles API errors.

UUID (e.g. 550e8400-e29b-41d4-a716-446655440000) is the most universally compatible format for distributed systems and is safe to expose publicly without revealing row counts. Integer (e.g. 1, 2, 3) is the simplest format, common in traditional relational databases. Slug (e.g. item-001) is a URL-friendly string identifier useful for content-type resources like articles or products where IDs appear in URLs.

Yes. The Download button saves the output as a .json file you can import directly as a test fixture in Jest, Vitest, Cypress, or any testing framework that supports JSON imports. The mock data is deterministically generated — the same configuration always produces the same output — so your tests remain stable across runs. You can also copy the JSON and paste it directly into tools like Postman, Insomnia, or Hoppscotch to mock server responses.