Free JSON Formatter & Validator

Format an API response for inspection

This JSON formatter parses your input in the browser and displays either indented or compact JSON. Use it to inspect nested API responses, prepare configuration examples, or identify invalid syntax. The formatting operation does not upload your JSON to a server.

Try a nested JSON example

Paste this compact response into the input:

{"product":{"name":"Notebook","price":12.5},"tags":["paper","office"],"available":true}

With Prettify selected and indentation set to 2, the result is:

{
  "product": {
    "name": "Notebook",
    "price": 12.5
  },
  "tags": [
    "paper",
    "office"
  ],
  "available": true
}

Choose Minify to remove indentation and line breaks outside strings. Spaces within strings remain part of the value. Formatting helps you read the structure; minifying makes the representation more compact.

Fix common JSON syntax errors

Invalid input	Problem	Correct JSON
{'name':'Ada'}	Single quotes are not JSON string delimiters	{"name":"Ada"}
{"count":3,}	Trailing comma	{"count":3}
{enabled:true}	Object keys require double quotes	{"enabled":true}
{"value":undefined}	undefined is not a JSON value	{"value":null} if null matches your intended data

JSON also rejects comments. Remove comments before pasting a JavaScript configuration object. A parsing error describes invalid syntax; its wording and position information depend on your browser. The formatter does not automatically repair invalid input or decide what missing values should mean.

What this validator checks

The tool uses JavaScript's JSON.parse and JSON.stringify. It checks whether the input is valid JSON syntax, then serializes the parsed value. Objects, arrays, strings, numbers, booleans, and null can all be valid inputs.

This is not JSON Schema validation. A response such as {"price":"free"} is syntactically valid even when your application expects price to be a number. Check required fields and application rules separately. See the JSON.parse documentation for parser behavior.

Limits to check before copying

• Very large integers can lose precision when parsed as JavaScript numbers. Keep identifiers as quoted strings when your data format permits it, or use a lossless JSON parser.
• Duplicate object keys are not preserved: parsing keeps the last value for a repeated key. Do not use this formatter to detect duplicate keys.
• Numeric spelling, whitespace, and some property ordering may change. Do not use reformatted output when you need byte-for-byte preservation, such as a signed payload.
• Large inputs can make the browser unresponsive. There is no file upload or streaming parser; use a local command-line tool for large datasets.

Related debugging tasks

If your response is Base64-encoded text, decode it with the Base64 Encoder / Decoder before validating the JSON. For two versions of a configuration, use the Text Difference Checker after formatting both with the same indentation. You can find other formatters in the free tools directory.

Use sanitized sample data when sharing results with teammates. Browser-side processing does not remove the need to protect API tokens or personal information in copied output.