WordPress.org

Requirements

• You need the reCAPTCHA keys here and/or the MailHide keys here
• If you plan on using MailHide, you will need to have the mcrypt PHP module loaded (Most servers do)
• If you turn on XHTML 1.0 Compliance you and your users will need to have Javascript enabled to see and complete the reCAPTCHA form
• Your theme must have a do_action('comment_form', $post->ID); call right before the end of your form (Right before the closing form tag). Most themes do.