JSON (JavaScript Object Notation) is the lingua franca of APIs and config files. This tool formats it for readability, minifies it for transport, and validates it — all in your browser, so sensitive data stays private.
Format vs minify
Formatting (pretty-printing) adds indentation and line breaks so JSON is easy to read and diff. Minifying strips all that whitespace to make the payload as small as possible. You'll format while developing and minify for production.
Validation rules to remember
Strict JSON requires double-quoted keys and strings, no trailing commas, and no comments. If your data breaks these rules it's technically not JSON — this validator will flag exactly where it fails to parse.
Frequently asked questions
No. All formatting and validation happens locally in your browser — your data never leaves your device.
It removes all optional whitespace, producing the smallest valid JSON on a single line — useful for reducing payload size.
Common causes are trailing commas, single quotes instead of double quotes, unquoted keys, or comments — none of which are allowed in strict JSON. The error message points to the position.