Mock JSON data generator
About Mock JSON Data Generator
The mock JSON data generator creates fake records from a simple field spec. Map each key to a type such as fullName, email, date.past or uuid, and get an array of 10, 50 or 100 populated objects.
Already have a JSON Schema? Switch From to JSON Schema and the generator builds one example document from it. It uses the schema's own examples, defaults and enums first, then the declared types and formats.
Use the dummy JSON data to seed a database, fill a UI prototype or write test fixtures without typing samples by hand. The values are made up, so there is no personal data involved. Runs in your browser. Nothing is uploaded.
How it works
Writing the field spec
The spec is a JSON object with a fields map, like { "fields": { "id": "uuid", "name": "fullName" } }. Each key becomes a property in every record, filled with a value of the chosen type. An unknown type returns an error that lists the supported ones.
Supported types
uuid, fullName, firstName, lastName, email, username, date.past, date.future, date.recent, number.int, number.float, boolean, city, country, company, phone, url, ipv4, color, lorem.word and lorem.sentence.
Choosing how many records
Pick 10, 50 or 100 with the Count control. It overrides any count set in the spec. Use a few records for a screenshot or 100 to test pagination and scrolling.
Same spec, same data
The generator uses a random generator seeded from your spec text, so the same spec always gives the same output. Change the spec, even by one character, to get a new set. Dates are ISO 8601 strings.
Sample JSON from a JSON Schema
In JSON Schema mode, const, default, examples, example and enum values win. Other fields get a value from their type, the minimum for numbers and a recognizable sample for formats like uuid, email, uri, date and date-time. Local $ref links starting with #/ are resolved, with protection against endless recursion.
Required fields and array length
Turn on Required only to get the smallest object the schema asks for. Array items sets how many elements each array gets, from 1 to 3. The first oneOf or anyOf branch is used, and simple allOf object parts are merged.
Frequently asked questions
What field types can I generate?
Names, usernames, emails, dates in the past, future or last week, integers, decimals, booleans, cities, countries, companies, phone numbers, URLs, IPv4 addresses, hex colors, lorem text and UUIDs. Map each key in your spec to one of these types.
How many records can I create at once?
Choose 10, 50 or 100 with the Count control. Every record follows the same spec, so the shape stays the same while the values vary.
Can I generate mock JSON from a JSON Schema?
Yes. Set From to JSON Schema and paste the schema. You get one example document built from its examples, defaults, enums, types and formats. It does not fetch external $ref URLs.
Is the dummy JSON data real?
No. Values are picked from built-in lists and random numbers, not taken from real people.
Are the generated UUIDs unique?
They are UUID v4-shaped values from a seeded generator, so they differ across records and are fine as test ids. They are not cryptographically random, so do not use them as production keys. Use the UUID generator for those.
Will a schema sample always pass validation?
Not for every schema. Patterns, conditionals and cross-field rules are not solved, and an example written in the schema can itself be invalid. Check important fixtures with your schema validator.
Is anything uploaded when I generate data?
No. Generation runs in your browser.
Sources & last verified
We checked this tool's behavior and the claims on this page against the specifications below on . The tool runs in your browser, so the output you see is exactly what the engine produced.
Found a wrong result or an outdated claim? Report an error and we will check it again.
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