JSON Formatter & Validator
Beautify, minify and validate JSON in your browser. Get the exact line and column of any syntax error, plus a colour-coded, readable result. Nothing is uploaded — your data never leaves your device.
Formatted JSON appears here…
How to Format & Validate JSON Online
- Paste your JSON into the left box, or click Sample to try it out.
- Click Format to pretty-print with your chosen indent, or Minify to strip every space and newline.
- If the JSON is invalid, the status bar shows the exact error, line and column and highlights the offending line so you can fix it fast.
- Use Copy or Download to take the clean result back to your code.
Format vs. Minify — What’s the Difference?
- Format (beautify) adds indentation and line breaks so a human can read and debug the structure.
- Minify removes all optional whitespace to make the file as small as possible — ideal for API payloads and production configs, where every byte counts.
- Both produce the same data; only the whitespace differs. Round-tripping never changes your values.
Why Is My JSON Invalid?
The most common reasons JSON fails to parse:
- Trailing commas —
{"a":1,}is invalid. JSON allows no comma after the last item. - Single quotes — keys and strings must use double quotes, not
'like this'. - Unquoted keys —
{name:"x"}must be{"name":"x"}. - Comments — standard JSON does not allow
//or/* */comments. - Undefined / NaN — only
true,falseandnullare valid keywords.
Frequently Asked Questions
Is my JSON uploaded anywhere?
No. Parsing, formatting and validation run entirely in your browser with JavaScript. Your data is never sent to a server, so it’s safe for API keys, tokens and private payloads.
What does the validator check?
It runs your text through the browser’s native JSON parser — the same rules servers use. If it parses, it’s valid RFC 8259 JSON; if not, you get the precise position of the first error.
Can it handle large files?
Yes — because everything is local, it comfortably formats files of several megabytes. Very large documents depend on your device’s memory rather than any upload limit.
Does formatting change my data?
Never. Formatting and minifying only add or remove whitespace. Every key, value, number and boolean stays exactly the same.