Sargas

Integrate Google reCAPTCHA on your website. Protect the Login, Registration, Lost Password and Comments forms. 
Plugin also supports Woocommerce, Mailchimp for WordPress, Ninja Forms Contact Form and Gravity Forms plugins.
<h4>Features:</h4>
<ul>
<li>Add reCAPTCHA to:
<ul>
<li>Login form</li>
<li>Registration form</li>
<li>Lost Password form</li>
<li>Comments form</li>
<li>MailChimp for WordPress</li>
<li>WooCommerce:
<ul>
<li>Login form</li>
<li>Registration form</li>
<li>Lost password form</li>
<li>Checkout form</li>
</ul>
</li>
<li>Ninja Forms Contact Form</li>
<li>Gravity Forms</li>
</ul>
</li>
</ul>

Sargas reCAPTCHA

reCAPTCHA for login, signup, comment, WooCommerce, Mailchimp and other forms.

llavillaccama

The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms. It protects your website from spam by means of math logic, easily understood by human beings. 
This captcha can be used for login, registration, comments forms.
This plugin is based on the recapcha of google, for receive more information can visit the website: https://www.google.com/recaptcha
<a href="http://webdesignjc.com/recaptchawp/index.html" rel="nofollow ugc">Support</a>

JC Recaptcha

The Add new recaptcha google plugin allows you to implement a super security REcaptcha form into web forms.

Sargas reCAPTCHA vs JC Recaptcha