Is this a JSON formatter?

The page is a validator. If the input is valid, you can copy pretty-printed JSON. The primary job is pointing at the first syntax error.

Why did my JSON fail?

Trailing commas, single quotes, and comments are common. JSON.parse rejects all three.

Do you upload the document?

No. Validation is JSON.parse in the browser.

Can I validate NDJSON?

This page expects one JSON value. For line-delimited JSON, use the JSON to CSV converter, which parses NDJSON line by line.

Not supported. This tool is RFC 8259 JSON only.

Runs in your browser · Last updated 4 September 2026

JSON Validator

Validate JSON and see the exact line and column of the first syntax error. Optionally pretty-print valid input.

JSON

Valid JSON

{
  "ok": true,
  "items": [
    1,
    2,
    3
  ],
  "note": "Trailing commas fail JSON.parse"
}

How to use this tool

Paste a JSON value.
If it is invalid, read the error line and column.
If it is valid, copy the pretty-printed output.
Send a valid array of objects to JSON to CSV when you need a spreadsheet.

Worked example

Add a trailing comma after the last item in the sample, like [1, 2, 3,]. The validator should fail and report a position near the comma. Remove the comma and it pretty-prints again.

Frequently asked questions

Is this a JSON formatter?: The page is a validator. If the input is valid, you can copy pretty-printed JSON. The primary job is pointing at the first syntax error.
Why did my JSON fail?: Trailing commas, single quotes, and comments are common. JSON.parse rejects all three.
Do you upload the document?: No. Validation is JSON.parse in the browser.
Can I validate NDJSON?: This page expects one JSON value. For line-delimited JSON, use the JSON to CSV converter, which parses NDJSON line by line.
What about JSON5?: Not supported. This tool is RFC 8259 JSON only.