Fumiki Takahashi

TAROSKY INC.

Hametuha INC.

This plugin adds a block to your block editor. 
This block changes its display depending on a current user’s capability.
<ul>
<li>You can set capability for block.</li>
<li>If a current user has a capability for the block, its content will be replaced.</li>
<li>Or else, block is displayed as log in link.</li>
<li>This block is an inner block, so you can nest any blocks inside it. Convert it to a reusable block for your productivity.</li>
</ul>
See screenshot for how block will be displayed.
This plugin use REST API to convert block content, so you can use it with cached WordPress. 
Even if you use CDN like <a href="https://aws.amazon.com/cloudfront/" rel="nofollow ugc">CloudFront</a> or <a href="https://www.cloudflare.com/" rel="nofollow ugc">Cloudflare</a>, this plugin displays proper contents for each users.
For performance enhancement, <a href="https://wordpress.org/plugins/cookie-tasting/" rel="ugc">Cookie Tasting</a> is recommended. 
It decrease server access including REST API by checking COOKIE value before accessing to server side script.

For Your Eyes Only

Add a restricted block for specified users.

Chase Wiseman

Whatever your reasons, you may need your site’s visitors to confirm their age before viewing the content of your site. Age Verify does just that. It’s a simple plugin that lets you specify a minimum age and add an age-gate between a potential visitor and your content, just to be safe. Enjoy!

Age Verify

Like my review on another similar plugin, because this plugin uses PHP to check cookies, it doesn't work with cached pages...such as with the W3 Total Cache plugin or WP Engine.

Would be better with Javascript

A simple way to ask visitors for their age before viewing your content.

For Your Eyes Only vs Age Verify