Mock Data Generator
Build fake API responses and table fixtures in your browser. Choose a user or measurement preset, or describe fields as a JSON array. The same seed, schema and row count produce the same records, making a test case easy to repeat. Names use a small example list and email addresses use example.com.
Key features
- JSON arrays or CSV with CRLF record separators
- 1–1,000 records and up to 20 custom fields
- ID, name, email, integer, number, boolean, date, UUID-shaped and constant fields
- Repeatable seeded output and optional CSV text formula protection
How to use
- Choose Users or Measurements, or select Custom schema to use the input area.
- Set the row count, seed and JSON or CSV output format.
- For a custom schema, enter an array of objects with name and type properties.
- Run the generator, inspect the result and copy it into your test file. Keep CSV text protection enabled when appropriate.
Use cases
- Prepare API responses for tables and pagination
- Test CSV import with quotes, line breaks and formula-shaped strings
- Create repeatable fixtures for reproducing an application bug
Frequently asked questions
How do I write a custom schema?
Enter a JSON array with name and type for each field. Types are id, name, email, integer, number, boolean, date, uuid and constant. Integer accepts min and max; constant requires a string, number, boolean or null value. Nested objects and array constants are unsupported.
What numeric and date ranges are generated?
Integer defaults to 0–999; you may set integer min and max within -1,000,000 to 1,000,000. Number generates two-decimal values from 0 to 999.99. Dates range from 2020-01-01 through 2030-12-31. IDs start at 1.
Does the same seed always produce the same result?
With this implementation, the same seed, profile or schema, and row count reproduce the same values. Changing field order or types changes how random values are consumed. The generator is unsuitable for passwords or security randomness.
Does this create real people or accounts?
No. Names come from a short example list and emails use the reserved example.com domain. The uuid field uses repeatable randomness in UUID v4 format; it is not intended for production identifiers or guaranteed uniqueness.
What does CSV formula protection do?
The default adds an apostrophe before text cells and headers that start with formula characters such as =, +, - or @. Negative numeric values are unchanged. Raw mode preserves the text, which a spreadsheet may interpret as a formula; check your import settings.
Why are some numbers or large results rejected?
The tool rejects JSON numbers whose decimal value would round or underflow to zero when parsed. Use string constants for long precise numbers. Schemas are limited to 100,000 characters and output to 1,000,000 characters to bound browser work.
Privacy
The schema, seed and generated records are processed in your current browser. This tool does not send them to a server or write them to browser storage. Copying writes to the clipboard only when you request it.
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