JSON Formatter & Validator

About JSON Formatter & Validator

JSON Formatter & Validator pretty-prints, minifies and validates JSON online. Paste or type into the editor and the output is formatted with 2-space indentation as you go; if the JSON is invalid, the parser error message tells you what went wrong. Click Minify to strip whitespace for compact payloads, and the output stays minified as you keep editing until you click Format again. You can upload a .json file, copy the result, or download it as formatted.json. Large integers such as 64-bit IDs keep their exact digits instead of being rounded. Developers use it to debug API responses, clean up config files and check JSON syntax. Your JSON is processed in your browser and never sent to a server.

How to use

1. Paste JSON into the Input editor, or click Upload JSON to load a .json file from your device.
2. The Output editor shows the formatted JSON automatically; click Format for 2-space indentation or Minify to compress it onto one line; the chosen mode stays active while you edit.
3. If the JSON is invalid, read the error message shown above the editors to locate the problem.
4. Click Copy above the output to copy the result, or Download to save it as formatted.json.
5. Click CLEAR to empty both editors and start over.

Limitations & notes

• Duplicate keys are not flagged; only the last value for each key is kept in the output.
• Numbers are normalized when reformatted, for example 1.0 becomes 1 and 1e3 becomes 1000.
• Keys named "__proto__" or "constructor" (and keys that merely contain those words) are kept as ordinary keys, the same as native JSON.parse; they cannot alter any object prototype.
• While the input is invalid, the output is cleared, so Copy and Download never hand out a stale result.

FAQ

How do I validate JSON?

Paste it into the input editor. If it parses, the formatted result appears on the right; if not, an error message describes the problem.

Why is my JSON invalid?

The most common causes are trailing commas, single quotes instead of double quotes, unquoted keys, and comments. Standard JSON allows none of these.

What is the difference between formatting and minifying JSON?

Formatting adds line breaks and indentation so humans can read it. Minifying removes all unnecessary whitespace to make the payload as small as possible; the data itself is identical.

Will large numbers lose precision?

No. The formatter uses a big-number-aware parser, so integers beyond JavaScript's safe range (such as 64-bit IDs) keep their exact digits.