Format, validate, or minify — locally
Paste JSON on the left and pick what you need. Format pretty-prints it with the indentation you choose, so a wall of minified text becomes readable. Minify strips every space and line break for the smallest payload. Validate just checks whether it parses, and if it doesn't, tells you where it broke.
Why "runs in your browser" matters here
The JSON a developer pastes into a formatter is rarely a toy example. It's a debug response, a config file, an API payload — and it often carries auth tokens, customer records, or internal hostnames. Most online formatters send that text to a server to process it. This one doesn't: the work is done by JSON.parse and JSON.stringify in your own tab. You can prove it — turn off your Wi-Fi after the page loads and it keeps working.
If you've already pasted a real payload into a tool you're unsure about, treat any secrets in it as exposed and rotate them. Our guide What you're actually pasting into an online JSON formatter walks through how to check a tool and what to do next.
Reading the error message
When JSON is invalid, the browser reports the first thing it couldn't parse — a trailing comma, a missing quote, a stray bracket. Common causes:
- Trailing commas —
[1, 2, 3,]is valid in JavaScript but not in JSON. - Single quotes — JSON strings and keys must use double quotes.
- Unquoted keys —
{name: "x"}must be{"name": "x"}. - Comments — JSON has none; strip
//and/* */first.
Frequently asked questions
Is my data sent anywhere?
No. There is no server call — parsing and formatting happen entirely in your browser. That's the whole point of this tool, and the airplane-mode test above proves it.
Can it handle large files?
Yes, within your device's memory. Very large payloads (tens of megabytes) may pause briefly while your browser parses them, but nothing is uploaded, so there's no size limit imposed by a server.
Does formatting change my data?
No. Formatting and minifying only change whitespace. Keys, values, order and types come out exactly as they went in — it's the same JSON, laid out differently.
Tools that pair with this one
- QR Code Generator — turn a small JSON config or link into a scannable code, also in your browser.
- Word Counter — count characters in a string field when a limit matters.
Everything runs locally in your browser. Keep a copy of your original before minifying anything you can't easily regenerate.