JSON formatter and validator
Paste raw JSON to pretty-print it, validate syntax, or minify it for production. Runs entirely in your browser.
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Output
What is JSON and why does formatting matter?
JSON (JavaScript Object Notation) is the de-facto standard for data interchange on the modern web. APIs, configuration files, NoSQL databases, and almost every web service use JSON to transmit structured data. Raw JSON from an API response is often minified, all whitespace stripped, to reduce payload size, which makes it completely unreadable to humans.
Pretty-printing (or "formatting") JSON re-inserts indentation and line breaks to reveal the structure clearly. When debugging an API integration, reviewing a configuration file, or exploring an unfamiliar data schema, formatted JSON can reduce investigation time from minutes to seconds by making nesting, keys, and values instantly visible.
Minifying JSON reverses this process, removing all unnecessary whitespace to reduce file size before deploying to production. For a large JSON payload, minification can cut transfer size by 15-30%, directly improving API response times and page load performance. The validate function checks JSON syntax without reformatting, which is useful for continuous integration checks or a quick sanity test before committing a config file.
This tool runs entirely in your browser using the native JSON.parse and JSON.stringify methods. Nothing is sent to a server, paste sensitive API responses without concern.
Frequently asked questions
Does this support JSON5 or JSONC?
No, this tool validates and formats standard JSON (RFC 8259) only. JSON5 and JSONC (JSON with comments) are supersets not accepted by native JSON.parse.
Is there a size limit?
Browser memory is the only limit. JSON under 10 MB will format instantly. Very large payloads may cause the page to slow down on low-end devices.
How do I copy the output?
Click into the output textarea and press Ctrl+A then Ctrl+C (or Cmd+A, Cmd+C on Mac) to select and copy all output text.