Free JSON Generator Online — Generate Mock JSON Data Instantly

Number of Records

Fields

What Is a JSON Generator?

A JSON generator is a tool that creates realistic-looking but entirely fake JSON data based on a schema you define. It's used whenever you need sample data fast — for API testing, front-end prototyping, seeding a development database, or writing unit tests without touching real records. Instead of handwriting JSON arrays by hand, you define the field names and types and let the tool do the repetitive work. This approach is at the heart of libraries like Faker.js, which programmatically generates names, emails, addresses, and more. The JSON specification (RFC 8259) defines the exact grammar your generated data will conform to, and the MDN JSON API reference explains how browsers parse and stringify it natively. For more advanced schema-driven generation, the JSON Schema specification lets you define types, constraints, and validation rules that generation tools can use to produce valid shaped data. Online tools like Mockaroo popularised browser-based test data generation, and this tool brings the same idea to a fast, schema-first, no-signup workflow.

How to Use the JSON Generator

Set the Record Count

Enter how many JSON objects you want — between 1 and 100. Each object will be one element in the output array.

Define Your Schema

Add, rename, and configure fields. Each field needs a name and a type. Use the Add Field button to grow your schema and the X button to remove any field you don't need.

Generate, Copy, or Download

Click Generate to produce the JSON array. Use Copy to put the result on your clipboard, or Download to save it as a .json file.

Frequently Asked Questions

What field types are supported?

Nine types are available: string (random word), number (0–99), boolean (true/false), email (user###@example.com), name (common first name), uuid (RFC 4122 v4 UUID), date (ISO date string within the past year), url (https://example.com/page-###), and phone (+1-###-###-####).

Is the generated data random every time?

Yes. Each time you click Generate, fresh random values are produced using Math.random() and crypto.randomUUID(). There's no seed or caching, so results differ on every run.

Can I generate nested objects?

Not directly from the UI — the schema builder creates flat objects. For nested structures, generate a flat array first, then manually edit the JSON in a JSON Editor.

What is a JSON generator used for?

Common use cases include: seeding a development or staging database with realistic-looking records, mocking API responses during front-end development, generating fixture files for automated tests, and populating UI components when the real back-end isn't ready yet.

Does this tool run in the browser only?

Yes. All data generation happens locally in JavaScript — nothing is uploaded to a server. That makes it safe to use when your schema contains sensitive field names, and it works entirely offline once the page is loaded.

JSON Generator — Generate Mock JSON Data