application/json. JSON filenames use the extension
Douglas Crockford originally specified the JSON format in the early 2000s; two competing standards, RFC 8259 and ECMA-404, defined it in 2017. The ECMA standard describes only the allowed syntax, whereas the RFC covers some security and interoperability considerations.
A restricted profile of JSON, known as I-JSON (short for "Internet JSON"), seeks to overcome some of the interoperability problems with JSON. It is defined in RFC 7493.