JSON Validator and Formatter

If you work with APIs, config files, or any kind of structured data, you’ve almost certainly run into a JSON error at some point — a missing comma, an unquoted key, a stray bracket — and spent longer than you’d like squinting at a wall of text trying to find it. That’s exactly the problem we built this tool to solve.

Kings Tools is a free online JSON formatter and validator. Paste your JSON in, and in a fraction of a second you’ll know whether it’s valid, exactly where it breaks if it isn’t, and you can beautify or minify it depending on what you need it for. No sign-up, no file upload, no software to install — it runs entirely in your browser.

Below, we’ll walk through how to use the tool, what actually makes JSON valid or invalid, how JSON validation compares across different environments (command line, code editors, and a few popular programming languages), and answer the most common questions we hear about JSON formatting and validation.
What This Tool Does

Our JSON formatter and validator online tool has three modes, and you can switch between them instantly:

Beautify (Format) — Takes minified, compressed, or just messily-indented JSON and reformats it into clean, properly indented, human-readable structure. This is the mode most people reach for when they’ve copied a JSON response from an API or a log file and need to actually read it.

Minify — The opposite operation. Strips out all unnecessary whitespace, line breaks, and indentation to produce the smallest possible JSON payload. Useful when you’re preparing JSON for production use, reducing file size for a config, or optimizing an API response.

Validate — Checks whether your JSON is syntactically correct according to the JSON specification, and if it isn’t, tells you the specific line and column where the parser broke. This is the mode that answers the question “is this JSON valid?” without you having to guess — essentially a JSON checker built directly into the page.
We were frustrated by JSON tools that buried a simple utility behind ads, logins, or interfaces that hadn’t been updated in years. Kings Tools exists to be the tool we wanted to use ourselves: fast, private, and focused on doing one job — formatting and validating JSON — properly.

Does this tool fix invalid JSON automatically?

Not automatically — we intentionally show you where the error is rather than guessing at a fix, since auto-correcting could silently change your data in ways you didn’t intend. Once you know the exact location, fixing trailing commas or missing quotes is usually a quick manual edit.