I want to setup security challenge google re-captcha front of my site without any form. for example, if a visitor try to visit on my site (http://domain.com) they need to pass security challenge(google captcha) without filling any form. and when he/she passed security challenge the security page will move him automatically to the main page of my site (http://domain.com/wellcome). can someone help me how I don this?
From their documentation it seems there are several ways of checking. If I read correctly by adding a data attribute (data-callback) with your javascript function name in, it will be called once they have been verified.
https://developers.google.com/recaptcha/docs/verify
So you could use a function that then redirects them like:
function redirect(){
window.location = "http://domain.com/welcome";
}