Short answer: paste your JSON, click Format, and the page pretty-prints it with indentation and an exact error position if something is wrong. It runs entirely in your browser — the text never leaves the tab.
Output appears here.It takes a string of JSON and parses it with the browser's own JSON engine, then prints the same data back out in a chosen shape. Beautify adds two-space indentation and line breaks so a person can read the structure. Minify strips all whitespace so the data is as short as possible before it goes into a request or a file. Both steps start from a correct parse, so a formatter is really a reader and rewriter, not a repair tool.
Same data, two shapes:
// beautified — human reads this
{
"name": "Ada",
"skills": ["math", "code"]
}
// minified — shipped in a request
{"name":"Ada","skills":["math","code"]}
Use beautify when you are editing or reading; use minify when size matters and a human will not look at it again.
A formatter cannot rewrite invalid JSON, because there is nothing valid to rewrite. What it can do is pinpoint the failure. When the parse fails it reports the line and column of the offending character — usually a missing comma between values, an unquoted key, a single quote where JSON requires a double, or a trailing comma after the last item. Fix that spot by hand and re-run; the next error, if any, will be the next real one.
This formatter is plain JavaScript with no backend. The text you paste is read by the page and rewritten in place; nothing is transmitted to a server. The same check the site uses elsewhere applies here too: open DevTools, watch the Network tab while you format something, and count what leaves — a genuinely local tool produces none. That is the whole reason the tool is shipped as static HTML and JavaScript: there is no server that could receive your text.
.jsonc or a JavaScript literal, strip those first; strict JSON allows neither.Related: Claude's watermark, explained · the two layers: what can and cannot be removed · strip image metadata before sharing · what Google actually marks · Claude vs ChatGPT: what each lab marks
Paste the JSON into the box and click Format. The page parses it with the browser's own JSON engine and reprints it with two-space indentation and sorted, readable structure. Everything runs in the tab — there is no server, so the text never leaves the page.
No. The formatter is plain JavaScript with no backend. The text you paste is read by the page and rewritten in place; nothing is sent to a server, and there is no network request carrying your content. You can confirm this yourself with the browser DevTools Network tab while formatting a file: it shows no upload.
It reports the error, it does not repair it. A formatter can only reprint JSON that is already valid. If the input has a missing comma, an unquoted key, or a trailing comma, parsing fails and the tool shows the exact line and column of the problem so you can fix it by hand. It will not guess at what you meant.
Beautify (pretty-print) adds indentation and line breaks so a human can read the structure. Minify removes all whitespace so the same data takes the fewest possible characters, which is what you want before shipping JSON inside a request or a file. Both start from a valid parse, so both require the input to be correct first.
An unexpected token means the parser hit a character it could not place at that point — most often a missing comma between values, an unquoted key, a single quote instead of a double quote, or a trailing comma after the last item. The formatter reports the line and column of the offending character, which is usually the spot to look first.