Why isn't possible to add the reCaptcha to the login page?
A lot of customers asked us why is possible to add the reCaptcha to the registration form but not to the login form. What we always ask is "why you should do that?".
This request comes likely from a wrong comprehension of the reCaptcha system. I guess that if you want to add the reCaptcha to the login form is to prevent a brute-force attack, but this isn't the correct way to do it. Let's try to make a clarification.
Why you can add a reCaptcha on the registration form?
ReCaptcha is used to avoid that fake accounts are created by a bot on your site. In this way only real accounts will be registered.
If you want to prevent brute-force attacks on your login page, reCaptcha isn't the solution your are looking for.
How can I prevent brute-force attack?
There are many useful security plugin that provide this feature. Some examples easy to use and much powerful than a reCaptcha: