Viktor Androshuck

This lightweight plugin automatically scans the content of your posts and pages and adds <code>rel="nofollow noopener noreferrer"</code> to all external links. 
Internal links are untouched. Improves SEO and security with zero configuration.
<ul>
<li>No admin panel needed</li>
<li>Safe and fast</li>
<li>Does not affect internal links</li>
<li>Helps comply with SEO best practices</li>
</ul>

Auto External Link Nofollow


Does exactly what it says on the tin! No fluff, just "no follow" external links across your site 👍


Great Plugin

Automatically adds rel="nofollow noopener noreferrer" to all external links in post and page content.

perceptionsystemlabs

Now you can simply filter your content Using Ajax Post Content Filter. Ajax Post Content Filter allows you to filter your content with dropdown box. Just install the plugin, activate and open the ACF Posts located in the left side menu bar. You need to add new ACF posts by filling up the post title and placing your content in the editor then publish it. Simply put the shortcode [ACF] in a page or post in admin or you can put the shortcode ajax_content_filter(); in your template file . You will got the simple dropdown box on your page at front side. Just select your post created in the plugin’s post and you’ll get the content of your particular post.
<h3>Shortcode</h3>
Our free plugin comes with short code support, so the following two short codes will get the same result. 
Want a shortcode in wordpress admin ? Use the following shortcode. 
[ACF] 
and to use shortcode in a template file, Use this 
ajax_content_filter();

Auto External Link Nofollow vs Ajax Content Filter