Phil

There are many uses for restricting content based on age, be it movie trailers, beer or other adult themes. This plugin allows you to set a restriction on what content can been seen or restricted based on the age of the user.
Features
<ul>
<li>Ask users to verify their age on page load</li>
<li>SEO Friendly – common bots and crawlers are omitted from age checks</li>
<li>Ability to add custom user agents for less common bots</li>
<li>Shortcode for in content restrictions</li>
<li>Choose to restrict an entire site, or selected content</li>
<li>Select a different age on individual content</li>
<li>Allow certain content to not be age gated under “all content” mode</li>
<li>Three choices for input; dropdowns, input fields or a simple yes/no button</li>
<li>Customise the order of the inputs based on your region (DD MM YYYY or MM DD YYYY)</li>
<li>Allow a “remember me” check box if desired</li>
<li>Ability to omit logged in users from being checked</li>
<li>Add your own logo</li>
<li>Update the text displayed on the entry form</li>
<li>Select background colour/image, foreground colour and text colour</li>
<li>Use built in styling out of the box, or your own custom style</li>
<li>Ability to add legal note or information to the bottom of the form</li>
<li>Redirect failed logins to a URL of your choice e.g. an alcohol awareness website.</li>
<li>Ability to use a non caching version</li>
<li>Various hooks to add even more customisation such as additional form fields</li>
<li>Compatible with multilingual plugins WPML, Polylang (2.3+), WP Multilang</li>
</ul>

Age Gate

the plugin does it's job properly, but it spams the dashboard with nags about next version age gate; you click dismiss and it's back there... very very annoying.

spamming dashboard with announcements

A plugin to check the age of a visitor before view site or specified content

mindgeekcy

MyDirtyHobby Affiliate Plugin to be used by amateurs to sign up users via their own WordPress sites.

Age Gate vs MyDirtyHobby Affiliates