JSON Data Generator

How to use it

1. Write the JSON you want — objects, arrays, and plain values — as strict, double-quoted JSON. Wherever a value should be fake, type a token like {{fullName}}, {{email}}, or {{uuid}}.
2. Reach for the palette instead of typing: it groups all 31 tokens. The numeric ones take a range — {{integer(1,100)}}, {{amount(5,500)}} — and {{words(4)}} sets a length.
3. For a list, shape the array as ["{{repeat(3)}}", <item>]: the first slot is the count, the second is the template to repeat. Nest a repeat inside an item for child arrays, and use {{index}} for the row number.
4. Leave the seed blank for a fresh random batch — the seed used shows in a chip — or pin a number so the output never changes.
5. Press Generate, or ⌘/Ctrl + Enter, then toggle pretty or compact and copy or download the .json. Share folds template and seed into one link.

Paste a JSON shape, drop a few double-brace tokens into it, and this tool fills them with fake data — names, emails, UUIDs, numbers, dates, and more. Wrap any item in a repeat() and you get an array of that shape. Every run is seeded, so the same template and seed rebuild byte-for-byte identical JSON, and the whole thing runs here in your browser.

Examples

["{{repeat(3)}}",{"id":"{{uuid}}","name":"{{fullName}}"}]

[
  {
    "id": "5fb9220d-9b0f-4d32-a248-6492457c3890",
    "name": "Tracey Schowalter-Haag"
  },
  {
    "id": "a7170e4a-4882-4fcf-8e9e-130564d5482c",
    "name": "Clotilde Schultz"
  },
  {
    "id": "bc151d95-145b-4ae7-81bc-8c786010a58e",
    "name": "Danika Greenfelder"
  }
]

{"n":"{{integer(1,10)}}","b":"{{boolean}}","lat":"{{latitude}}","amt":"{{amount(5,100)}}","label":"user-{{integer(1,9)}}"}

{
  "n": 7,
  "b": true,
  "lat": -49.1668,
  "amt": 57.38,
  "label": "user-7"
}

["{{repeat(2)}}",{"team":"{{company}}","members":["{{repeat(2)}}",{"name":"{{firstName}}","idx":"{{index}}"}]}]

[
  {
    "team": "Bartell, Gulgowski and Adams-Russel",
    "members": [
      {
        "name": "Jeremy",
        "idx": 0
      },
      {
        "name": "Wendell",
        "idx": 1
      }
    ]
  },
  {
    "team": "Effertz LLC",
    "members": [
      {
        "name": "Reilly",
        "idx": 0
      },
      {
        "name": "Astrid",
        "idx": 1
      }
    ]
  }
]

{"score":"{{integer(5,1)}}"}

Token "integer" range is inverted: the first number must be less than or equal to the second.

Every example on this page is executed against the same engine that powers the tool, on every build.

Common errors

Expected double-quoted property name in JSON at position 7 (line 1 column 8)

The template is parsed as strict JSON, so a trailing comma, a single quote, or an unquoted key stops it — and the message names the exact position, which the editor can jump to.

Unknown token "fullname". Tokens are case-sensitive — check spelling and see the token palette.

Tokens are spelled exactly as the palette lists them, and case matters: {{fullname}} is unknown where {{fullName}} is not. The message echoes back the id it could not place.

Token "integer" expects 2 argument(s) but got 0.

Ranged tokens need their numbers: {{integer}} and {{integer(1)}} are refused where {{integer(1,100)}} works. The same rule governs {{float}} and {{amount}}.

{{repeat(n)}} must be the first element of a two-item array, like ["{{repeat(3)}}", <template>].

repeat() is structural, not a value — it only works as the first of exactly two array elements. A repeat token anywhere else, or in an array of three, is refused.

This template would generate too many items — a single repeat() is capped at 1,000 and the whole template at 50,000. Lower a repeat() count or split the template.

The total is estimated from the repeat counts before any data is drawn, so an oversized request fails fast. Nested repeats multiply, which is how a modest-looking template can blow past the cap.

Keyboard shortcuts

⌘/Ctrl + Enter

Generate JSON from the current template (mints a seed if blank).

⌘/Ctrl + S

Download the generated JSON as a .json file.

⌘/Ctrl + C

Copy the output when nothing is selected and it is under 1 MB.

⌘/Ctrl + Shift + C

Copy the output even while a selection exists.

t

Cycle the color theme.

? or ⌘/Ctrl + /

Open the shortcut help dialog.

Esc

Close the open dialog.