JSON formatter
Format, validate and minify JSON — without pasting it into someone else’s server.
Why this one runs locally
Pasting an API response into an online JSON viewer is one of the most casually risky habits in software. That response very often contains a bearer token, a session identifier, a customer’s email address, or an internal endpoint — and pasting it means posting all of it to a server you know nothing about, usually from a work machine, usually while debugging something urgent. It never feels like exfiltration at the time.
This formatter uses the JSON parser already built into your browser. The text you paste stays in the tab, and there is no request that could carry it anywhere.
Questions
Is my JSON sent anywhere?
No. Parsing and formatting happen in your browser with the built-in JSON engine. Nothing is transmitted, which is the reason to use this rather than a typical online formatter — API responses routinely contain tokens, email addresses and customer records.
Why does my JSON fail to parse when it looks fine?
The usual causes are a trailing comma after the last item, single quotes instead of double quotes, unquoted keys, or a comment. JSON allows none of those, even though JavaScript does. The error message points at the line and column so you can see which it is.
What does minifying do?
It removes every space and line break that is not inside a string, producing the smallest valid representation of the same data. It is what you want when embedding JSON in a request body or a config file where size matters.
Does it handle large files?
Up to a few megabytes comfortably. Beyond that the browser slows down noticeably and you will get a message suggesting a smaller extract rather than a frozen tab.
Are keys reordered or values changed?
Key order is preserved as it appears in the input. Numbers are normalised by the JSON engine, so 1.50 becomes 1.5 and 1e3 becomes 1000 — the values are identical, the spelling is canonical.