JSON Validator & Beautifier

About JSON validator & beautifier

This tool checks whether text is strictly valid JSON and, if it is, rewrites it with clean indentation. You can also collapse it to a single line. When the text is broken you get the parser's own error message so you can find the stray comma or missing quote.

How to use it

1. Paste your data into the JSON Input box.
2. Choose 2, 4 or 8 spaces from the Indent Size menu.
3. Click Validate & Format to check the syntax and pretty-print it, or click Minify to compress it onto one line.
4. If the text is invalid, read the red message that starts with Invalid JSON.
5. Use the Copy button on the Formatted JSON card to take the result with you.

Formatting with 2 spaces, and what a round trip can change

{"id":12345678901234567890,"name":"Ada","tags":["a","b"],"x":1.0}

{
  "id": 12345678901234567000,
  "name": "Ada",
  "tags": [
    "a",
    "b"
  ],
  "x": 1
}

When to use it

• Finding the exact spot where an API response or config file fails to parse.
• Making a minified webhook payload readable before you debug it.
• Squeezing a formatted config down to one line for an environment variable.
• Normalizing indentation so two JSON files produce a clean line-by-line comparison.

Questions about JSON validator & beautifier

Why is my long ID different in the output?

JavaScript stores numbers as 64-bit floats, so integers beyond 9,007,199,254,740,991 lose precision when parsed and rewritten. Keep such IDs as strings in the source data to avoid silent changes.

Are comments and trailing commas accepted?

No. This is strict JSON, so comments, trailing commas, single-quoted strings and unquoted keys are all reported as errors. Those features belong to JSON5 or JavaScript object literals.

What happens to duplicate keys?

The parser keeps only the last value for a repeated key, and the earlier ones vanish from the output without a warning. Search your input for repeats if a value looks wrong after formatting.

Why does the wording of an error differ between browsers?

The message comes straight from the browser's built-in parser, so Chrome, Firefox and Safari each phrase it their own way. The position they report is usually the useful part.

Does formatting reorder my keys?

Mostly no, but keys that look like whole numbers, such as 2 or 10, are moved to the front in ascending order. That is standard JavaScript object behavior and does not change the meaning.

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