🧾 JSON Formatter & Validator

What is this tool for?

Paste any JSON payload - from an API response, a config file, or logs - and instantly pretty-print it with readable 2-space indentation, or minify it down to a single compact line. Invalid JSON is caught immediately with a clear error message describing exactly what's wrong, so you can fix malformed data without guessing.

Reading the error message

The validator is the browser's own JSON parser, so the error is exact rather than a guess: it names the unexpected character and the position where parsing stopped. The mistake is almost always just before that position. The three classics: a trailing comma after the last item, single quotes instead of double, and a comment - JSON allows none of those, by specification, even though JavaScript allows all three. That is not this tool being strict; it is what makes JSON portable.

When to format, when to minify

Format when a human needs to read it: debugging an API response, reviewing a config, comparing two payloads. Minify when a machine needs to carry it: embedding JSON in a URL, an environment variable, or a request body where every byte is billed or logged. The two buttons are inverses - formatting a minified payload and minifying it again gives you back the same bytes.

Limits

Everything runs locally, so file size is limited by your machine, not a server - multi-megabyte payloads are fine. The key count includes nested keys at every depth, which is why it can exceed the line count. What the tool will not do: repair broken JSON for you, sort keys, or accept JSON5 and YAML. It validates the standard, nothing looser.