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.