Scott Reilly

This plugin allows you to restrict the usernames that new users may use when registering for your site.
If open registration is enabled for your site (via Settings -> General -> Membership (“Anyone can register”)), WordPress allows visitors to register for an account on your blog. By default, any username they choose is allowed so long as it isn’t an already existing account and it doesn’t include invalid (i.e. non-alphanumeric) characters.
Possible reasons for wanting to restrict certain usernames:
<ul>
<li>Prevent usernames that contain foul, offensive, or otherwise undesired words</li>
<li>Prevent squatting on usernames that you may want to use in the future (but don’t want to actually create the account for just yet) (essentially placing a hold on the username)</li>
<li>Prevent official-sounding usernames from being used (i.e. help, support, pr, info, sales)</li>
<li>Prevent official username syntax from being used (i.e. if all of your administrators use a prefix to identify themselves, you don’t want a visitor to use that prefix)</li>
<li>Prevent spaces from being used in a username (which WordPress allows by default)</li>
<li>Require that a username starts with, ends with, or contain one of a set of substrings (i.e. “support_”, “admin_”)</li>
<li>Require a minimum number of characters for usernames</li>
<li>Limit usernames to a maximum number of characters</li>
</ul>
When attempting to register with a restricted username, the visitor will be given an error notice that says: 
ERROR: This username is invalid. Please enter a valid username.
NOTE: This plugin does not put any restrictions on usernames that the admin chooses for users when creating user accounts from within the WordPress admin. This only restricts the names that users choose themselves when registering for your site.
SPECIAL NOTE: Many membership plugins implement their own user registration handling that often bypasses checks (and hooks) performed by WordPress. As such, it is unlikely that the plugin is compatible with them without special plugin-specific amendments.
Compatible with Multisite and BuddyPress as well.
Links: <a href="http://coffee2code.com/wp-plugins/restrict-usernames/" rel="nofollow ugc">Plugin Homepage</a> | <a href="https://wordpress.org/plugins/restrict-usernames/" rel="ugc">Plugin Directory Page</a> | <a href="https://github.com/coffee2code/restrict-usernames/" rel="nofollow ugc">GitHub</a> | <a href="http://coffee2code.com" rel="nofollow ugc">Author Homepage</a>
<h3>Hooks</h3>
The plugin exposes one filter for hooking. Typically, customizations utilizing this hook would be put into your active theme’s functions.php file, or used by another plugin.
c2c_restrict_usernames-validate (filter)
The ‘c2c_restrict_usernames-validate’ hook allows you to add your own customized checks for the username being registered. You can add additional restrictions or override the assessment performed by the plugin.
Arguments:
<ul>
<li>$valid (boolean): The assessment by the plugin about the validity of the username based on settings. True means username can be used.</li>
<li>$username (string): The username being registered.</li>
<li>$settings (array): The plugin’s settings.</li>
</ul>
Example:
<pre><code>/**
 * Add custom checks on usernames.
 *
 * Specifically, prevent use of usernames ending in numbers.
 *
 * @param bool $valid True if the username is valid, false if not.
 * @param string $username The username.
 * @param array $options Plugin options.
 */
function my_restrict_usernames_check( $valid, $username, $options ) {
 // Only do additional checking if the plugin has already performed its
 // checks and deemed the username valid.
 if ( $valid ) {
 // Don't allow usernames to end in numbers.
 if ( preg_match( '/[0-9]+$/', $username ) ) {
 $valid = false;
 }
 }
 return $valid;
}
add_filter( 'c2c_restrict_usernames-validate', 'my_restrict_usernames_check', 10, 3 );
</code></pre>

Restrict Usernames

Restrict the usernames that new users may use when registering for your site.

Freemius

RelyWP

Elliot Sowersby / RelyWP

Better Coupon Restrictions adds additional restrictions and options to your WooCommerce coupons.
When enabled, you will see a new “Better Coupon Restrictions” tab in the coupon edit screen.
From there, you can set the following additional restrictions:
<ul>
<li>
Improved Product Restrictions: This section improves the default product usage restrictions allowing you to set a minimum and maximum quantity for each.
</li>
<li>
Product Category Restrictions: This section improves the default product category usage restrictions allowing you to set a minimum and maximum quantity for each.
</li>
<li>
Cart Restrictions: This section allows you to set restrictions based that cart quantity, subtotal, and total weight.
</li>
<li>
Date Restrictions: This section allows you to set restrictions based on the current date including a date range, select months, or weekdays.
</li>
<li>
Customer Status Restrictions: This section allows you to set restrictions based on the customer’s status including if they are a new customer, or their logged in status.
</li>
<li>
User Role Restrictions: This section allows you to set restrictions based on the customer’s user role.
</li>
</ul>
<h3>PRO Version</h3>
The PRO version of Better Coupon Restrictions includes the following additional features:
<ul>
<li>
Customer Address Restrictions: This section allows you to set restrictions based on the customer’s billing and shipping address. You can also set a maximum use per address.
</li>
<li>
Customer Order History Restrictions: This section allows you to set restrictions based on the customer’s order history including their total spent and total orders.
</li>
<li>
Time Since Last Order Restrictions: This section allows you to set restrictions based on the time since the customer’s last order.
</li>
<li>
Time Registered Restrictions: This section allows you to set restrictions based on the time since the customer registered.
</li>
<li>
Referring Domain Restrictions: This section allows you to set restrictions based on the referring domain.
</li>
<li>
IP Address Restrictions: This section allows you to set restrictions based on the customer’s IP address including allowed and disallowed IP addresses, along with a usage limit per IP.
</li>
<li>
Meta Data Restrictions: This section allows you to set restrictions based on the customer’s meta data.
</li>
<li>
Cookie Restrictions: This section allows you to set restrictions based on the customer’s cookies.
</li>
</ul>
<a href="https://relywp.com/plugins/better-coupon-restrictions/" rel="nofollow ugc">Learn more about Better Coupon Restrictions PRO</a>

Better Coupon Restrictions for WooCommerce

Additional restrictions and options for your WooCommerce coupons.

Restrict Usernames vs Better Coupon Restrictions for WooCommerce