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JSON Formatter & Beautifier

Paste minified or malformed JSON. Instantly format, validate, and view it with clean indentation. Also minifies in one click.

JSON Formatter & Validator

Common JSON mistakes and how to fix them

  • Single quotes instead of double quotes — JSON requires "double quotes" for strings and keys. Single quotes ('like this') are not valid JSON.
  • Trailing commas — {"a":1,} is invalid. Remove the comma after the last item in any array or object.
  • Unquoted keys — {name: "John"} is JavaScript object notation, not JSON. Keys must be quoted: {"name": "John"}.
  • Comments — JSON does not support comments. // this or /* this */ will cause a parse error.
  • NaN and Infinity — these are JavaScript values, not valid JSON. Replace with null or a numeric string.

Frequently Asked Questions

No. Everything is processed locally by JavaScript inside your browser tab. Your JSON — including any API keys, passwords, or sensitive data it might contain — never leaves your device. You can verify this by opening DevTools → Network tab and watching that no requests fire when you click Format.
JSON (JavaScript Object Notation) is a data format derived from JavaScript syntax, but it's stricter. JSON only allows strings, numbers, booleans, null, arrays, and objects. JavaScript objects also allow functions, undefined, and symbols. In JSON, all keys and string values must use double quotes. This strictness is what makes JSON a reliable transport format for any language — not just JavaScript.
Minify when you're sending JSON over a network and want to reduce payload size. A minified JSON file is typically 10–30% smaller than the formatted version since all whitespace is removed. For configuration files you edit by hand, keep them formatted for readability. For API responses and stored data files that are only read programmatically, minified is fine — though gzip compression at the transport layer usually reduces size more than minification does.