Free · No sign-up · Runs in your browser
JSON Formatter & Validator
Paste JSON to format it readably, minify it for transport, or validate it. Invalid JSON produces a specific error message telling you what went wrong and where, rather than a silent failure.
Input
Output
What the tool does
- Format — indents nested structures with 2 spaces, 4 spaces, or tabs so the shape of the data is visible.
- Minify — strips all whitespace for the smallest possible payload.
- Validate — any parse failure reports the specific problem and its position.
- Sort keys — orders object keys alphabetically at every level, which makes two API responses directly comparable in a diff.
The JSON mistakes that cause most errors
- Trailing commas.
{"a": 1,}is invalid. Legal in JavaScript, never in JSON — the most common error by a wide margin. - Single quotes. JSON requires double quotes for both keys and string values.
- Unquoted keys.
{name: "Ada"}is a JavaScript object literal, not JSON. - Comments. JSON has no comment syntax.
//and/* */are both invalid. - Special values.
NaN,Infinity, andundefinedare not valid JSON. Usenull. - Unescaped characters. Literal newlines and unescaped double quotes inside strings must be written as
\nand\".
Why formatting locally matters
API responses routinely contain access tokens, customer records, and internal identifiers. Many online JSON formatters send your input to a server to process it, which means pasting a production response into one is a genuine data disclosure. This tool parses everything with the browser's native JSON engine — no request is made, and you can confirm that in your network tab.