JSON Formatter & Validator
Paste JSON, get it pretty-printed, validated or minified — with exact error positions. Nothing leaves your browser.
Your files never leave your device.
How to use the JSON formatter
- Paste your JSON into the box — an API response, a config file, a payload you're debugging.
- Format pretty-prints with 2-space indentation. Minify strips whitespace for production. Validate checks syntax and reports the exact line and column of any error.
- Copy or download the result.
Why a local formatter?
The JSON you paste into formatters is rarely neutral: it contains API keys, internal URLs, user data, production configs. Pasting that into a random website means sending it to someone else's server — most tools do exactly that, even if they don't tell you. This one runs entirely on your device: JSON.parse and JSON.stringify in your own browser tab. Watch the Network tab in dev tools while you work if you want proof.
It's also faster. No upload, no server round trip, no queue — validation of a malformed payload reports the exact error position instantly, the same way your editor does.
When a formatter earns its keep
Debugging API responses: a minified 200 KB payload is unreadable until it's pretty-printed — then the wrong field name is obvious in seconds. Config review: docker-compose, tsconfig.json, package.json and friends are easier to diff when formatted consistently. Data handoffs: minify before sending to keep payloads small and unambiguous. And because validation reports exact line and column, you spend your time fixing the error rather than finding it.
The errors this catches (and what they mean)
- Trailing commas —
{"a": 1,}is legal in JavaScript, illegal in JSON. - Single quotes — JSON strings must use double quotes.
- Unquoted keys —
{name: "x"}must be{"name": "x"}. - Comments — JSON has no
//or/* */; that's JSONC/JSON5, a different format. - NaN / Infinity / undefined — not valid JSON values.
- Trailing data — anything after the closing bracket makes the document invalid.
On failure, the validator shows the position like "line 12, column 34" so you can jump straight to the problem instead of hunting through a minified wall of text.
Frequently asked questions
Is my JSON uploaded anywhere?
No. Formatting and validation run entirely in your browser. Nothing is sent to a server, logged or stored — safe for API keys, configs and production payloads.
What does the validator catch?
Any syntax error the JSON spec forbids: trailing commas, single quotes, unquoted keys, comments, missing brackets. On failure it reports the position (line and column) of the error.
Can I minify JSON?
Yes — the Minify button strips all non-essential whitespace, giving the smallest valid JSON for production use.
Is there a size limit?
No artificial limit. Formatting is instant for typical API responses and configs; extremely large files (tens of MB) depend on your device's memory.
Does it work offline?
Yes. Once the page has loaded, every feature works without an internet connection.