JSON Formatter & Validator

Paste JSON to reformat it with consistent indentation, validate it against the JSON specification, or strip it down to the smallest valid form. If the document is invalid, you get the exact line and column of the problem along with what the parser expected — rather than a bare "syntax error".

Formatting runs on our server and the result is returned in the same request. Nothing is stored: your JSON is never written to disk, never logged, and never shared with a third-party service.

How it works

The tool parses your input with PHP's JSON parser in strict mode, which follows RFC 8259. Valid documents are re-encoded with your chosen indentation, and the structure is walked to report depth, key count and array sizes — useful for spotting an unexpectedly deep nest or a payload far larger than you assumed.

Invalid documents are scanned to convert the parser's byte offset into a human line and column, and a short excerpt around the failure is shown so you can see the problem in context. The most common causes are trailing commas, single quotes instead of double quotes, unescaped control characters inside strings, and unquoted object keys — all of which JavaScript tolerates in object literals but JSON does not.

Frequently asked questions