Private, ad-free JSON workspace
Paste, import, or drop JSON to format messy data into readable, validated output. JSON Toolbox keeps the work in your browser, which makes it useful for API payloads, logs, fixtures, and config files you do not want to send to another server.
{"user":{"id":42,"name":"Ada","roles":["admin","editor"],"active":true},"updated":"2026-01-14T09:30:00Z"}{
"user": {
"id": 42,
"name": "Ada",
"roles": [
"admin",
"editor"
],
"active": true
},
"updated": "2026-01-14T09:30:00Z"
}A minified API response on the left, formatted with two-space indentation on the right.
JSON has a small and strict grammar. Keys and string values use double quotes, never single quotes. The only value types are strings, numbers, booleans, null, arrays, and objects, and you cannot leave a trailing comma after the last item in a list or object. Comments are not part of the format, which catches a lot of people who copy config files that allow them.
When the formatter refuses to indent your input, it is almost always one of those rules. The validator uses the same parser your browser uses, so the errors you see here line up with what your code would throw at runtime.
Formatting only adds or removes whitespace. Keys, values, and structure stay the same, so you can prettify a payload, read it, and paste it back into your app without worrying about drift. When you need the compact version again, the minifier reverses it.
JSON formatting and validation run client-side in your browser. Your JSON is not uploaded to JSON Toolbox servers.
Yes. The formatter runs in your browser, so pasted JSON is processed client-side instead of being uploaded for formatting.
Yes. The formatter detects invalid JSON and helps you find syntax problems while you work.
The usual culprits are single quotes instead of double quotes, a trailing comma after the last item, comments, or an unescaped character inside a string. Fix those and the formatter will indent it.
Yes. You can import JSON files, work with them in the editor, and download the formatted result.
No. Key order is preserved exactly as you pasted it. Only whitespace changes.
There is no fixed limit. Because everything runs locally, the practical ceiling is your browser's memory rather than an upload cap.
JSON Toolbox combines formatting with a developer workspace: multiple panels, file workflows, editor controls, JSONPath context, and an ad-free interface.