JSON Formatter & Validator
Paste any JSON to pretty-print it with 2 or 4 space indentation (or tabs), validate it, or minify it down to a single line. Errors point out exactly what's wrong. Everything runs locally in your browser.
Reviewed by Vincenzo Manto, Founder & Lead Developer · Last updated September 27, 2026
How it works
- 1
Paste or type your JSON into the input panel.
- 2
Choose 2-space, 4-space, tab indentation, or minify to one line.
- 3
Any syntax error is flagged immediately, pointing at the exact position.
- 4
Copy the formatted result or download it as a .json file.
Example
{"name":"Mario","roles":["admin","dev"],"active":true}{
"name": "Mario",
"roles": ["admin", "dev"],
"active": true
}Why format and validate JSON online?
API responses, config files, and log exports are often minified or malformed, making them unreadable at a glance. This tool re-indents any JSON payload instantly and points out the exact character where a syntax error breaks parsing, saving you from manually counting brackets in a text editor.
A formatter that never leaves your browser
Because the JSON.parse and stringify logic runs entirely client-side, you can safely paste API keys, internal configs, or production data without worrying about it being logged or stored anywhere. Close the tab and nothing remains.
Beyond formatting
Most online JSON formatters stop at pretty-printing. Once your JSON is clean, open it straight in our JSONPath tester to query a specific field, or in JSON to Parquet if the same data needs to land in an analytics pipeline, without re-pasting it anywhere.
Frequently asked questions
Does this tool send my JSON to a server?
No. Parsing, validating, and formatting all happen locally using your browser's JavaScript engine, so your data never leaves your device.
What exactly does the error message tell me?
When the JSON is invalid, the tool reports the character position and a description of what the parser expected there, so you can jump straight to the broken bracket, comma, or quote.
Can I minify JSON instead of formatting it?
Yes. Switch to the minify mode to collapse the same JSON into a single line with no extra whitespace, useful for shrinking payloads before sending them somewhere.
Does it support tabs instead of spaces?
Yes, the indentation selector includes 2 spaces, 4 spaces, and tab, so you can match your project's existing style.
Will it fix trailing commas or comments in my JSON?
No, the validator follows the strict JSON spec, so trailing commas, comments, and unquoted keys are reported as errors rather than silently corrected, since JSON.parse in the browser would reject them too.
Is there a size limit on the JSON I can paste?
There's no hard-coded limit, but very large documents (many megabytes) are bounded only by your browser's available memory since everything is processed client-side.