JSON Formatter & Validator
Paste JSON to pretty-print and validate it, or minify it — with clear error messages. Runs entirely in your browser.
About this tool
JSON is the standard format for APIs and config files, but a single misplaced comma or quote makes it invalid and hard to read. This formatter parses your JSON, validates it, and re-prints it with consistent indentation so the structure is easy to scan; if it cannot parse, it shows the exact error message so you can fix it. You can also minify — strip all whitespace — to produce the most compact form for transmission or storage. Everything happens in your browser using the built-in JSON parser, so your data is never uploaded. Use it to tidy up API responses, debug config files, or shrink JSON payloads.
How to use it
- Paste your JSON into the box.
- Click Format / Validate to pretty-print and check it.
- Choose an indent width, or click Minify for compact output.
- Copy the result.
Frequently asked questions
- How do I validate JSON?
- Paste it and click Format / Validate. If the JSON is well-formed it is re-printed neatly with a “Valid JSON” confirmation; if not, the exact parser error (and often the position) is shown so you can locate the problem.
- What does minifying JSON do?
- Minifying removes all unnecessary whitespace (spaces, newlines, indentation), producing the smallest valid representation. It is useful for reducing payload size in network requests or storage, where readability does not matter.
- Why is my JSON invalid?
- Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or comments — none of which are allowed in strict JSON. The error message points to where parsing failed.
- Is my JSON sent anywhere?
- No. The tool uses your browser’s native JSON parser entirely client-side. Your data never leaves your device, which keeps sensitive payloads private.
- Does it preserve key order and number precision?
- Key order is preserved as parsed. Numbers are handled by JavaScript’s parser, so extremely large integers beyond safe-integer range may lose precision — a JSON limitation, not specific to this tool.
- Can it handle large files?
- Yes, within your browser’s memory. Very large documents (tens of MB) may be slow to render but will format correctly. For huge files, a streaming parser or command-line tool is better.