The JSON Formatter was created to help with debugging. As JSON data is often output without line breaks to save space, it is extremely difficult to actually read and make sense of it. This little tool hoped to solve the problem by formatting the JSON data so that it is easy to read and debug by human beings.
Shortly after it was created, JSON validation was added following the description set out by Douglas Crockford of json.org in RFC 4627. It has since been expanded to also validate both current competing JSON standards RFC 7159 and ECMA-404.