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.

er11

e11 reCAPTCHA is a no-frills way to add Google’s reCAPTCHA widget to the standard WordPress comment form and/or the user registration page. By default it will require only logged-out users to solve CAPTCHAs on comments and new users to solve a CAPTCHA to successfully register on the site; it’s also possible to configure e11 reCAPTCHA to not require CAPTCHA solving in either of these two forms or to require it on comments by all users.

e11 reCAPTCHA

WordPress plugin to use reCAPTCHA to help protect comments and new user signups against spam.

F13 reCaptcha vs e11 reCAPTCHA