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JSON Formatter & Validator — Preserve Large Numbers
Turn a dense API response or an AI-generated JSON snippet into readable, indented text. This formatter checks JSON syntax, then changes only whitespace between tokens. Numeric digits and string escapes stay intact.
Calculations run in your browser. No account or API key is needed.
Your result
{
"project": "circle-tools",
"ready": true,
"id": 9007199254740993,
"sizes": [
1,
2,
3
]
}How to use this tool
Paste a complete JSON value without Markdown fences.
Choose two spaces, four spaces or compact output.
Format the JSON, inspect the result and copy it into your editor.
A useful structured-output check
Use this before putting a response into a test fixture, configuration file or debugging note. A valid result means the syntax is JSON; it does not establish that required fields, types or business rules are correct. Check those against your own schema.
Numbers remain text during formatting
For example, 9007199254740993 keeps every digit, and 1.00 retains its decimal spelling. The formatter also preserves duplicate keys and their order. Avoid duplicate keys in application data because different consumers can interpret them differently.
Common questions
Why does a JavaScript object fail validation?
JSON requires double-quoted property names and strings. Comments, undefined and trailing commas are not accepted.
Does formatting fix incorrect data?
No. It reveals the structure without guessing replacements or changing values. Correct invalid input in the editor and run it again.