JSON Formatter & Validator

What this tool checks

JSON looks like JavaScript but is stricter: keys must be double-quoted, trailing commas are not allowed, and values are limited to strings, numbers, booleans, null, objects and arrays. A single misplaced comma or a stray single-quote is enough to break a whole payload, and the resulting error from most languages' JSON parsers only gives a byte offset. This tool converts that into a line and column you can actually find, and beautifies valid JSON so nested structures are easy to read.

Minifying does the opposite: it strips every non-significant space and newline, which is what you want before sending JSON over the wire or pasting it into a field with a size limit.

Example

Paste a compact object:

{"name":"Ada","born":1815,"tags":["math","writer"]}

and Format produces:

{
  "name": "Ada",
  "born": 1815,
  "tags": [
    "math",
    "writer"
  ]
}

Common causes of invalid JSON

• Trailing commas — {"a": 1,} is valid in JavaScript object literals but not in JSON.
• Single-quoted strings or keys — JSON requires double quotes: {"a": 1}, not {'a': 1}.
• Unquoted keys — {a: 1} needs to be {"a": 1}.
• Comments — JSON has no comment syntax; // like this will fail to parse.
• NaN, Infinity or undefined — none of these are valid JSON values.

Doing the same thing in code

JavaScript

const pretty = JSON.stringify(JSON.parse(text), null, 2);
const compact = JSON.stringify(JSON.parse(text));

Python

import json
pretty = json.dumps(json.loads(text), indent=2)
compact = json.dumps(json.loads(text), separators=(",", ":"))