104 · Developer Tools

JSON Validator

Paste JSON to check it. If it’s invalid, you’ll see exactly where and why, with a pointer to the spot.

How to use the json validator

  1. Paste your JSON.
  2. Read the result: valid, or the line and column of the first error.
  3. Fix the error and check again.

The most common JSON mistakes

  • Trailing commas after the last item: [1, 2,].
  • Single quotes: JSON needs "double" quotes.
  • Unquoted keys: {name: 1} must be {"name": 1}.
  • Comments: JSON doesn’t allow // or /* */.
  • Missing commas between items.

Examples

{"a": 1,}

Trailing comma: remove the comma before “}”.

{'a': 1}

Expected a key in double quotes

Questions

What does the duplicate key warning mean?

JSON technically allows the same key twice in an object, but most parsers keep only the last value, which usually hides a bug.

Is my data uploaded?

No. Everything runs in your browser, so what you paste never leaves your device.