Format JSON

Worked example

Minified JSON from an API response,

{"id":42,"tags":["new","sale"],"price":{"amount":19.99,"currency":"EUR"}}

is formatted with consistent indentation:

{
  "id": 42,
  "tags": ["new", "sale"],
  "price": {
    "amount": 19.99,
    "currency": "EUR"
  }
}

The data itself is unchanged: formatting only adds whitespace between tokens.

When formatting fails

The formatter only accepts valid JSON. The most common problems are comments (// or /* */), trailing commas after the last item, single-quoted strings, unquoted keys, and values such as NaN or undefined. These are all allowed in JavaScript but not in JSON. Configuration files like tsconfig.json or VS Code settings use JSONC, a JSON-with-comments variant, and will be rejected until the comments are removed.

The JSON validator reports the document’s structure, depth, and number-range problems once the syntax is fixed. Keep your original when exact details matter: very large integers lose precision, and when a key appears twice, only its last value is kept.