JSON Formatter & Validator

How to format or validate JSON online

1. Paste a JSON object, array or other valid JSON value into the input area, or select Open JSON file.
2. Choose 2 spaces, 4 spaces or tabs, then select Format JSON for readable output. Select Minify JSON to remove unnecessary formatting whitespace.
3. To check syntax without changing the text, choose Validate only. If parsing fails, check the error message and any line and column information available from your browser.
4. Review the output, then copy it or download a .json file. Your original input remains available unless you deliberately replace it.

JSON formatting example

Pretty-printing makes nested data easier to inspect without adding or removing fields intentionally. For example, this minified input:

{"name":"Designs24hr","settings":{"active":true,"items":[1,2]}}

Becomes readable JSON with 2-space indentation:

{
  "name": "Designs24hr",
  "settings": {
    "active": true,
    "items": [
      1,
      2
    ]
  }
}

Format, validate or minify: which action do you need?

Common JSON syntax errors and how to check them

• Trailing comma: {"a":1,} is invalid JSON. Remove the comma before } or ].
• Unquoted key or single quotes: JSON requires double-quoted property names and string values.
• Missing separator: Separate fields and array entries with commas; use a colon between a property name and its value.
• Unclosed string or bracket: Check opening and closing quotation marks, braces and brackets.
• JavaScript comments and values: Standard JSON does not accept comments, undefined, NaN or Infinity.
• HTML instead of JSON: If an API response begins with <!DOCTYPE or <html, inspect the actual server response instead of attempting to format it as JSON.

A reported error location is where a parser noticed a problem; the typo may occur earlier. This tool never silently inserts missing punctuation or claims that malformed data has been repaired.

What validation and formatting cannot guarantee

A syntactically valid JSON document can still contain the wrong keys, invalid dates or data your application cannot accept. Browser parsing can also change certain representations when formatting or minifying: duplicate object keys are not retained as separate entries, very large JSON numbers may lose precision as JavaScript numbers, and numeric spelling such as 1.00 may become 1. Review critical financial or high-precision data before using rewritten output.

Browser processing takes place on your device in this tool; other scripts on a website can have their own data practices. Do not paste secret credentials or confidential datasets into any website without checking your organization's policies.

Frequently asked questions

Does this JSON validator fix invalid JSON?

No. It reports parsing errors and preserves the original input so you can correct it. It does not guess what a broken value or missing field should have been.

Can I format a JSON file?

Yes. Choose Open JSON file to read a local .json or text file in your browser. Very large files may slow down your device; the upload control limits files to 5 MB.

Why did a number or duplicate field change after formatting?

The tool parses and serializes JSON using browser JavaScript. That process can normalize number representations, lose precision in unusually large numbers and retain only one value for a repeated object key.

Can I validate a JSON string, number, boolean or null?

Yes. Valid JSON is not limited to objects and arrays; strings, numbers, booleans and null can also be valid top-level JSON values.

Is JSON formatting the same as JSON-to-CSV conversion?

No. This formatter keeps the result as JSON. To create spreadsheet-style rows from object data, use the JSON to CSV Converter.

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