Large JSON Dataset Generator

Runs in browser Test Data

Define a record template with placeholders ({{name}}, {{email}}, {{int:1-100}}, {{date}}) and generate up to 50,000 records, streamed into a downloadable file.

TEST DATA ONLY — all generated names, contacts, identifiers and numbers are synthetic and do not belong to real people or accounts.
Privacy: This tool runs entirely in your browser. Your input never leaves your device.

How to use Large JSON Dataset Generator

  1. Write one record as JSON with {{placeholders}} inside strings (or load the example).
  2. Set the number of records, shape and locale.
  3. Press Generate; use Download for large outputs.

Large JSON Dataset Generator features

  • Record template with 50+ placeholders: names, emails, phones, UUIDs, ints, floats, booleans, dates, picks, cities, companies, words…
  • Typed output — a lone placeholder becomes a number, boolean or null
  • Up to 50,000 records as an array, a paginated { data, total } envelope or JSON Lines
  • Automatic compact output above 2,000 records and a warning above 10,000
  • Preview table of the first 50 records and size summary
  • Seedable for reproducible fixtures

Large JSON Dataset Generator example

Template to records

Input:

{ "id": "{{index:1}}", "name": "{{fullName}}", "age": "{{int:18-65}}", "plan": "{{pick:free|pro}}" }

Output:

[
  { "id": 1, "name": "Sadie Price", "age": 37, "plan": "pro" },
  { "id": 2, "name": "Mia Kingsley", "age": 41, "plan": "free" }
]

Frequently asked questions about Large JSON Dataset Generator

Which placeholders can I use?

{{fullName}}, {{email}}, {{phone:SA}}, {{uuid}}, {{int:1-100}}, {{float:0-1:2}}, {{bool:80}}, {{date:2020-01-01,2024-12-31}}, {{datetime}}, {{pick:a|b|c}}, {{index:1}}, {{city}}, {{company}}, {{word}}, {{sentence}} and about forty more.

Do placeholders keep their type?

Yes. A string that consists of exactly one placeholder becomes a number, boolean or null when the generator returns one; placeholders inside longer text are interpolated as text.

How large can the output be?

Up to 50,000 records (about 20 MB with the sample template). Above 10,000 the tool warns and pretty-printing switches off above 2,000 records; use Download rather than Copy for big files.

Can I get JSON Lines or a paginated envelope?

Yes — choose the JSON Lines shape or the wrapped { data, total, page } envelope that mimics a paginated API.

Technical notes

Placeholders are resolved by the same field engine used by the CSV, XML and SQL generators, so {{int:1-100}}, {{float:0-1:3}}, {{date:2020-01-01,2024-12-31}} and {{pick:a|b}} behave identically everywhere. Person placeholders within one record share a single generated identity.