JSON Formatter & Validator Online — Free
Format, beautify, and validate JSON data with customizable indentation.
Frequently Asked Questions
How do I format JSON online?
Paste your minified or messy JSON into the input box. Our formatter instantly beautifies it with proper indentation. Choose 2 or 4 spaces for indent size.
Does this validate JSON?
Yes, our JSON formatter also validates your JSON syntax and provides clear error messages with line numbers if the JSON is invalid.
Can I minify JSON?
Yes, use the Minify button to remove all whitespace and produce compact, single-line JSON output — perfect for reducing payload size.
What is the difference between JSON formatter and JSON validator?
A JSON formatter beautifies the appearance of valid JSON with indentation. A JSON validator checks whether the JSON syntax is correct. Our tool does both simultaneously.
Is this JSON formatter free?
Yes, completely free with no usage limits, no sign-up required, and no ads that block your workflow. Your data stays in your browser.
Privacy First: All processing happens directly in your browser. Your data never leaves your device.
About JSON Format
JSON that arrives from an API is usually minified into a single line, which makes it unreadable the moment something goes wrong. Formatting it re-introduces the indentation and line breaks your eyes need, and validates the syntax at the same time.
What formatting actually does to your JSON
Beautifying JSON is a parse-then-print operation, not a text transformation. The input is parsed into an in-memory structure and re-serialised with your chosen indentation. That distinction matters: if the formatter returns output, your JSON is syntactically valid by definition. If it throws, you have a genuine syntax error rather than a cosmetic problem.
Because it is a full round-trip, key order is preserved but insignificant whitespace is discarded. Formatting is lossless with respect to data, never with respect to layout — comments are not part of the JSON specification and will be rejected outright.
Reading the error messages
Most JSON errors come from a handful of causes, and the browser error text points at a character offset rather than at the mistake. These are the ones worth recognising on sight:
- Unexpected token } in JSON at position N — almost always a trailing comma after the final element of an object or array. JSON, unlike JavaScript, forbids them.
- Unexpected token in JSON — single-quoted strings. JSON requires double quotes on both keys and string values.
- Unexpected end of JSON input — a truncated payload, usually a response that was cut off or a missing closing brace.
- Unexpected token N in JSON at position 0 — the response was not JSON at all. An HTML error page from a proxy is the usual culprit.
- Bad control character in string literal — a raw newline or tab inside a string that should have been escaped.
Minify or beautify?
Beautify while you are reading or debugging; minify before you ship. Minified JSON strips every byte of insignificant whitespace, which on a large API response is routinely 20 to 30 percent of the payload. Over the wire that matters, and gzip does not make it irrelevant — compression works better on the smaller input too.
Configuration files committed to git are the exception. Keep those formatted: a diff on a minified single-line file shows the entire file as changed, which destroys code review.