In short: A JSON formatter parses JSON text, reports the exact line and column of any syntax error, and re-prints valid JSON with consistent indentation — or minifies it to one line.
About JSON Formatter & Validator
JSON is easy for machines to read and painful for people when it arrives as one 40,000-character line from an API, a log file or a config dump. This formatter re-indents it so the structure is obvious, tells you straight away whether it is valid, and can shrink it back down when you need to paste it somewhere compact.
When parsing fails, you get the line and column of the problem plus a short preview of the text around it, so you can spot the stray trailing comma, the single-quoted key or the missing bracket without counting characters. Parsing uses your browser’s own JSON engine, so the verdict matches what JavaScript will do with the same text, and nothing you paste is sent anywhere.
How to use JSON Formatter & Validator
- Paste or type your JSON into the input box.
- Pick an indent size (2 spaces, 4 spaces or tabs) and tick Sort keys if you want object keys in alphabetical order.
- Press Format for readable output or Minify for the smallest single-line version.
- Copy the result or download it as a
.jsonfile. If the input is invalid, fix the spot shown in the error message and try again.
Examples
Input: {"id":7,"tags":["a","b"],"owner":{"name":"Ana"}}
Output with 2-space indent puts each key on its own line and nests owner one level deeper, which makes it easy to read and diff.
Input: {"a": 1, "b": 2,}
Result: an error pointing at line 1 near the closing brace. JSON does not allow a comma after the last item, even though JavaScript object literals do.
Frequently asked questions
Is my JSON sent to a server?
No. Formatting and validation happen entirely in your browser with JavaScript. You can load the page, disconnect from the internet and it still works.
Why does my JSON fail even though it works in JavaScript?
JavaScript object literals are more forgiving than JSON. JSON requires double-quoted keys and strings, forbids trailing commas, comments, undefined, NaN and single quotes. The error position shows where the parser stopped.
Does sorting keys change my data?
Only the order of keys inside objects changes. Values, arrays and array order are untouched, and JSON objects are unordered by definition, so the meaning stays the same.
How large a file can I format?
Several megabytes is fine on a normal laptop. Very large files (50 MB and up) depend on your device’s memory, since everything is processed locally.
Will large numbers lose precision?
Integers bigger than 253 (about 9 quadrillion) cannot be represented exactly by JavaScript, so formatting may round them. If you work with 64-bit IDs, keep them as strings in your JSON.
Updated November 2026 · Free, no signup · How we build and test tools