f13dev

Add Google reCaptcha to the comments section on blog posts. Requires Google reCaptcha v2 Checkbox API key.
Simple configuration via the admin settings page: 
* reCaptcha public key 
* reCaptcha private key 
* enable reCaptcha for (Everyone | Visitors | Nobody [disabled])
Additional hooks for programmers: 
$v = apply_filters(‘f13_recaptcha_add’); 
Will place a reCaptcha checkbox in the desired place.
$validate = apply_filters(‘f13_recaptcha_validate’); 
if (!empty($validate)) { 
 $v = $validate 
 // reCaptcha failed 
} else { 
 // reCaptcah passed 
}

F13 reCaptcha

Add Google reCaptcha to the comments section on blog posts. Additional hooks for adding reCaptcha to custom forms.

bonafidetech

The “Google reCaptcha for WordPress” is a perfect security solution to protect your website from spam and abuse.
<h4>Features / Highlights</h4>
<ul>
<li>Easy to customize, setup and use</li>
<li>Mobile friendly</li>
<li>Add reCAPTCHA to WordPress login form</li>
<li>Add reCAPTCHA to WordPress Registration form</li>
<li>Add reCAPTCHA to WordPress Lost Password form</li>
<li>Add reCAPTCHA to Comments submit the form</li>
<li>Add reCAPTCHA to WooCommerce login form</li>
<li>Add reCAPTCHA to WooCommerce Registration form</li>
<li>Supports multiple reCAPTCHA’s on same page</li>
<li>Many settings to let your work easy: reCAPTCHA size, theme, type and error message. You can read more about such settings on this <a href="https://developers.google.com/recaptcha/docs/settings" rel="nofollow ugc">URL</a></li>
<li>Change language from English to your desired one easily with a small snippet of code</li>
</ul>
<h3>Documentation</h3>
http://codeinstinct.com/bftgr/documentation/

Bonafide Tech Google Recaptcha for WordPress

The "Google reCaptcha for WordPress" is a perfect security solution to protect your website from spam and abuse.

F13 reCaptcha vs Bonafide Tech Google Recaptcha for WordPress