JavaScript Object to JSON Converter (JSON5 Validator)

A JavaScript object literal copied from code — unquoted keys, single quotes, comments, trailing commas, hex numbers — is not JSON, and JSON.parse rejects it. This converter reads the literal without running it and writes strict JSON, the same as JSON.stringify would produce. It understands everything in JSON5 plus common JavaScript extras such as template literals, numeric separators, BigInt and undefined, and tells you whether the input is valid JSON5, so it also works as a JSON5 validator.

How to use this tool

1. Paste the object, array or JSON5 text — a "const x =" declaration around it is fine.
2. Choose the indentation.
3. Decide how Infinity and NaN are written (JSON has no such numbers).
4. Copy the JSON; the "Input is" line says whether the input was strict JSON, JSON5 or JavaScript only.

Formula

{ key: 'v', } → {"key": "v"} · 0x1F → 31 · .5 → 0.5 · 1_000 → 1000 · undefined → left out · Infinity → null

JSON5 adds to JSON: identifier keys, single-quoted strings, escaped line breaks, \x escapes, comments, trailing commas, hexadecimal numbers, leading or trailing decimal points, a + sign, Infinity and NaN. JavaScript also allows template literals without ${…}, numeric separators, 0o/0b numbers, BigInt (10n), numeric keys and undefined; these convert but are reported as not JSON5. Numbers keep their digits, so long IDs are not rounded. Variables, function calls, shorthand properties and ${…} cannot be evaluated and are reported with their line and column — nothing is executed.

Example

The sample config becomes {"host": "localhost", "port": 8080, "content-type": "application/json", "retries": 3, "timeout": 0.5, …}: 0x3 becomes 3, .5 becomes 0.5, 1_000 becomes 1000, Infinity becomes null, the template literal becomes "Hello\nworld" and debug: undefined is dropped. "Input is" reports JavaScript only — not JSON5 because of the template literal, the numeric separator and undefined.