If you've built an HTML-only form using CallRail's form builder, there is a specific technical limitation that prevents the use of the reCAPTCHA field we offer in our form builder. Google's terms of service require any hostname for reCAPTCHA to be verified or whitelisted. For that reason, you're unable to use CallRail's reCAPTCHA field when you build an HTML-only form.
However, you can add your own reCAPTCHA to your HTML-only form once you've embedded the form on your website. We recommend installing reCAPTCHA v2 according to these instructions from Google:
If you prefer, you can install Google's reCAPTCHA v3 to your form using the instructions below: