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.

Todd Nestor

Hercules Recaptcha uses the latest Google Recaptcha API to more accurately determine if users are bots or not. 
If the user is not logged in it will display a Recaptcha for the user to fill out in the comment form. If the user 
disables javascript and is not logged in then comments will fail to submit.
The Recaptcha is also added to the registration page for both multisite setups and single blogs. There are options for 
having it show up on comments and/or the registration page, as well as options for its position on the comment form, and 
which style (Google gives only two options, dark or light).

Hercules Recaptcha

Hercules Recaptcha adds a Recaptcha to the comment form for non-logged in users.  It uses the latest Recaptcha API.

F13 reCaptcha vs Hercules Recaptcha