You need to Go to your google account https://www.google.com/recaptcha/intro/android.html Register your domain or list all your previous registered recaptcha domails https://www.google.com/recaptcha/admin#list
When your users submit the form where you integrated reCAPTCHA, you'll get as part of the payload a string with the name "g-recaptcha-response". In order to check whether Google has verified that user, send a POST request with these parameters: URL: https://www.google.com/recaptcha/api/siteverify secret (required) your-registerd-secret-key-by-google response (required) The value of 'g-recaptcha-response'. remoteip The end user's ip address.