When querying the state of the "I'm not a robot" user challenge, you have to make a POST request to https://www.google.com/recaptcha/api/siteverify passing your secret key and the response token to know the result of the challenge. But it is undocumented which Content-Types (MIME types) are supported. I guess every common MIME type is supported (application/x-www-form-urlenconded, application/json, application/xml), but, just for curiosity,
- Which are the
Content-Types supported bysiteverify? - Or is that "supported mime types" list for POST request standarized somehow?
I could not make application/json with a JSON encoded request function, but I was able to use application/x-www-form-urlencoded and verify it still works as it used to after substituting newer parameter names and https for http.
来源：https://stackoverflow.com/questions/39707075/google-recaptcha-v2-supported-content-types