nicolly

Convert all external links into internal or nofollow links!
This plugin is a fork of the hijacked and vulnarable “WP No External Links” plugin.
The following critical issues have been fixed: 
– Removed Cross-Site Scripting vulnerability. 
– Removed backdoor injected into original plugin. 
– Fixed creation of the new <code>links_stats</code> table: added charset collation and table existence check. 
– Fixed “Specified key was too long; max key length is 767 bytes” error on creating <code>mask_links</code> table. 
– Added removing tables on uninstallation.
No External Links plugin is designed for specialists who care about the number of outgoing links that can be found by search engines. Now you can make all external links internal! Plugin does not change anything in website database – it just processes the output. Now you don’t need to worry about your page rank dropping because of spam bots. You write any kind of http link and it becomes internal, hidden or nofollow! Of course, all the links will still be usable.
To make the long story short, your links like “http://gmail.com” will be masked into 
“http://YourBlog.com/goto/http://gmail.com” – or 
“http://YourBlog.com?goto=http://gmail.com”
<h4>Features</h4>
<ul>
<li>Masking links in posts, pages, comments or on the whole website including widget, theme footer, etc.</li>
<li>Outgoing clicks stats.</li>
<li>Javascript redirect with custom text and timeout.</li>
<li>Masking links with digital code and base64.</li>
<li>Completely removing links from your posts.</li>
<li>Custom redirects.</li>
<li>Disabling masking for registered users.</li>
<li>Disabling masking on per-post basis.</li>
<li>Using nofollow and noindex instead of redirection.</li>
<li>Excluding URLs from masking.</li>
<li>Masking links in custom fields.</li>
<li>Extending plugin with your own functions.</li>
</ul>
If you need any extra features, just create a ticket via support forum.
<h4>Known Issues</h4>
This plugin may conflict with your caching plugins, including Hyper Cache. Usually adding redirect page to caching plugin exclusions works fine.
If you disabled this plugin and still have links masked – check your chaching plugins.

WP No External Links

Convert all external links into internal or nofollow links!

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.

WP No External Links vs Auto External Link Nofollow