Sabaoh

This plugin will add some reCAPTCHA widget to login form, comment form, and user registration form. With this plugin, sites owners can avoid spam comment, user registration, and biting password.
Mighty CAPTCHA uses a Google reCAPTCHA technology. To work, API key pair, issued Google, is necessary.
For more information about key pair, please refer https://www.google.com/recaptcha/intro/index.html .
You can choose which form will be with reCAPTCHA widget or not. For login form and user registration form, a normal size widget is too wide. So you can choose compact widget. (but I do not like it.)
Below is characteristic of new Google reCAPTCHA.
<ul>
<li>Easy for ordinary users. They only must check the “I’m not a robot”.</li>
<li>When Google reCAPTCHA recognized an access was smell fishy, image authentication screen would appear.</li>
<li>New image authentication screen is without deformed letters, with photo images instead of them.</li>
<li>Photo images authentication is for example “choose all photos of a cat”. Easy to human and hard to robot.</li>
<li>It’s easy to use with smart phone or tablet.</li>
</ul>
Why don’t you usher it into your site!

Mighty CAPTCHA

Mighty-CAPTCHA add an authentication with Google reCAPTCHA technology to login, comment, and register form, with API keys which delivered by Google.

keycapability

Justin Fletcher

The ‘Network Subsite User Registration’ (NSUR) plugin removes the WordPress Multisite restriction that registration is on the Network main site, subsite Administrators can now allow user registration for their site only.
WordPress Network (Multisite) installations by default only allow user registration for the whole Network, e.g. users can only register for the main site and not the other sites on the network. The ‘Network Subsite User Registration’ plugin allows local admins of sub-sites within the Network/Multisite the ability to enable user registration themselves for their site.
The role by default that a new user receives is ‘subscriber’, however, there is a setting which allows you to define a different initial role (per sub-site) that a user receives after registration.
@Developers – If you want to use your own template you can override the template used for the ../local-signup page by creating a template with the file ‘page-signup.php’ and add this to either the parent or child theme.
<h4>Plugin site</h4>
<a href="https://justinandco.com/plugins/network-subsite-user-registration/" rel="nofollow ugc">https://justinandco.com/plugins/network-subsite-user-registration/</a>
<h4>GitHub – Development</h4>
<a href="https://github.com/justinticktock/network-subsite-user-registration" rel="nofollow ugc">https://github.com/justinticktock/network-subsite-user-registration</a>

Network Subsite User Registration

This plug-in works great to handle a situation that Wordpress should just do out of the box.  I would be hard pressed to make multi-site usable without it.

So simple, but a huge time savings


Ideal for maintaining control over users.


Work as imagined

Allow the public to register user accounts on Subsites within a Network (MultiSite) installation.

Mighty CAPTCHA vs Network Subsite User Registration