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.

dessky

Dessky reCAPTCHA is the lightweight WordPress plugin for website protection against spam comments and brute-force attacks. As name suggests it is protecting your website by adding Google’s reCAPTCHA to the login, comment, registration and forgot password forms.
This plugin was developed by <a href="https://dessky.com/" rel="nofollow ugc">Dessky Team</a>.
Dessky Team does not provide support for the Dessky reCAPTCHA on the WordPress.org forums. In order to get support or make a suggestion from a Dessky Team you will have to Join Our Open Community and <a href="https://discuss.dessky.org/t/dessky-recaptcha" rel="nofollow ugc">Start a Discussion</a>.
<a href="https://discuss.dessky.org/t/dessky-recaptcha" rel="nofollow ugc">DISCUSS WITH THE DESSKY TEAM</a>
<a href="https://discuss.dessky.org/t/dessky-recaptcha" rel="nofollow ugc">JOIN OUR OPEN COMMUNITY</a>: The purpose of this open community is to have a collective place where the community can help each other, and we can get some feedback to improve Dessky reCAPTCHA as well. Joining the community is also a great way to connect with like-minded people and share your experience.
You can also <a href="https://dessky.me/" rel="nofollow ugc">GET THE PREMIUM SUPPORT</a>
<a href="https://dessky.org/" rel="nofollow ugc">User Documentation</a>: Although Dessky reCAPTCHA is already easy to set up, we’ve put together tutorials, guides, and some knowledge bases to help you set up and get started with it.
I have further questions, how do I contact you?
Please fill up the <a href="https://dessky.com/contact/" rel="nofollow ugc">contact form</a> and we would be more than happy to assist.
<h4>What is protected with Google reCAPTCHA?</h4>
<ul>
<li>Comment form</li>
<li>Forgot password form</li>
<li>Registration form</li>
<li>Login form</li>
</ul>
You can select in admin where reCAPTCHA will be required.
<h4>Credits</h4>
Dessky reCAPTCHA is based on the ‘Simple Google reCAPTCHA’ plugin developed by <a href="https://profiles.wordpress.org/minor/" rel="nofollow ugc">Minor</a>.

Dessky reCAPTCHA

Protect your website against spam bots with reCAPTCHA.

F13 reCaptcha vs Dessky reCAPTCHA