JSON Formatter & Validator
Format, validate, and minify JSON — with clear error messages for invalid input.
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How to use this calculator
- 1
Paste your JSON into the text area.
- 2
Choose an action: format (prettify), minify, or validate.
- 3
If the JSON is invalid, the exact error message is shown.
Frequently asked questions
What is the difference between format and minify?
Formatting (beautifying) adds indentation and line breaks to make JSON human-readable. Minifying removes all whitespace to reduce file size — useful for APIs and storage.
What makes JSON invalid?
Common issues: trailing commas (not allowed in JSON), single quotes instead of double quotes for strings, unquoted keys, missing commas between array items, and comments (JSON does not support comments).
Is my data processed on your server?
No — all JSON processing happens in your browser using JavaScript's built-in JSON.parse() and JSON.stringify(). Nothing is sent to a server.
JSON formatting and validation
Valid vs well-formed JSON
JSON (JavaScript Object Notation) has strict syntax: keys must be double-quoted strings, arrays use square brackets, objects use curly braces, trailing commas are not allowed, and comments are not supported. This tool validates these rules precisely.
Format vs minify
Formatted JSON is for development and debugging — easy to read and edit. Minified JSON is for production — removes whitespace to minimize bytes transferred. A 10KB formatted JSON might minify to 6KB, saving 40% in API responses.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →