JSON Formatter & Validator

Copy output

About this tool

Paste JSON to check that it is valid and to reformat it with consistent indentation, or minify it onto a single line. It is handy for reading an API response, a log entry or a config file that arrives as one long line.

The output updates as you type. Everything runs in your browser, so you can paste JSON that contains tokens or personal data without it being uploaded.

Example

Input:
{"user":{"id":7,"name":"Mika","roles":["admin","dev"]},"active":true}

Formatted (2 spaces):
{
  "user": {
    "id": 7,
    "name": "Mika",
    "roles": [
      "admin",
      "dev"
    ]
  },
  "active": true
}

What formatting changes

This tool parses your JSON and writes it out again, so the result is equivalent JSON but not always a byte-for-byte copy of your data. In particular:

• Very large integers lose precision. Numbers are parsed as 64-bit floating-point values, so 12345678901234567890 becomes 12345678901234567000. If you handle IDs of that size, keep them as strings.
• Numbers are normalized: 1.0 becomes 1, 1e3 becomes 1000, and 1.50 becomes 1.5.
• Escaped characters are decoded: "é" is written as "é".
• If an object repeats a key, only the last value is kept.
• Keys that look like whole numbers (such as "1" or "2") are moved to the front in ascending order, as JavaScript objects do. Other keys keep their original order unless you turn on Sort keys.

Common syntax errors

• A trailing comma after the last item, as in {"a":1,}
• Unquoted or single-quoted keys and strings, as in {a:1} or {'a':1}
• Comments, which JSON does not allow
• undefined, NaN and Infinity, which are not valid JSON values

FAQ