WebFactory

Opens external links in a new tab or a or new window. You can set URLs that should either be forced to open in a new window or ignored.
The plugin produces XHTML Strict compliant code and is search engine optimized (SEO). 
This is done using JavaScript’s <code>window.open()</code>-function. It adds only a few lines of vanilla JavaScript to the page, and does not require any external libraries like jQuery.
Most other plugins perform a hack by altering the <code>target</code> parameter (i.e. <code><a href="http://somewhere.example" target="_blank"></code>). That method is not XHTML Strict compliant. 
This plugin handles the links client-side, which lets search engines follow the links properly. Also, if a browser does not support JavaScript, the plugin is simply inactive, and does not result in any errors.
If you need a more advanced plugin, with more options try our <a href="https://wordpress.org/plugins/wp-external-links/" rel="ugc">free WP External Links</a> plugin.
Credits 
Inspired by the <a href="http://www.zappelfillip.de/2005-12-05/zap_newwindow/" rel="nofollow ugc">Zap_NewWindow</a> plugin by <a href="http://www.zappelfillip.de/" title="His website is mostly in German" rel="nofollow ugc">Tom Köhler</a>. 
The banner is a <a href="http://www.flickr.com/photos/monja/1367946568/in/photostream/" rel="nofollow ugc">photo</a> by <a href="http://www.monja.it/" rel="nofollow ugc">Monja Da Riva</a>.
Translations 
Danish by <a href="https://kristianrisagerlarsen.dk" rel="nofollow ugc">Kristian Risager Larsen</a> 
Dutch by <a href="http://www.collectief-it.nl/" rel="nofollow ugc">Paul Staring</a> 
Lithuanian by <a href="http://Host1Free.com" rel="nofollow ugc">Vincent G</a> 
Other translations will be appreciated!
Known bugs 
The plugin conflicts with other plugins that change the links’ `onClick´ attribute.
Original developer 
Kristian Risager Larsen – <a href="http://kezze.dk" rel="nofollow ugc">kezze.dk</a>

External Links in New Window / New Tab

Open external links in a new window or new tab. SEO optimized and XHTML Strict compliant.

Cristi Tamas

Cristian Outbound Manager is a lightweight and reliable plugin that automatically handles all outbound/external links on your WordPress site. Improve SEO, security and user experience with zero effort.
Once activated, the plugin scans your post content and applies the attributes you choose:
<ul>
<li>Open external links in a new tab (<code>target="_blank"</code>)</li>
<li>Add <code>rel="nofollow"</code></li>
<li>Add <code>rel="noopener noreferrer"</code> for security</li>
<li>Exclude specific domains from being modified</li>
</ul>
Perfect for blogs, business sites, affiliate sites, WooCommerce stores and any website that uses outbound links.
This plugin is fully compatible with PHP 7.4 – 8.4.
<h3>Features</h3>
<ul>
<li>Automatically detect outbound/external links</li>
<li>Add <code>target="_blank"</code> to open links in a new tab</li>
<li>Add <code>rel="nofollow"</code> to external links</li>
<li>Add <code>rel="noopener noreferrer"</code> for security</li>
<li>Exclude domains (one per line)</li>
<li>Lightweight and fast — no impact on performance</li>
<li>Works with Gutenberg, Classic Editor, page builders and custom post types</li>
</ul>

Cristian Outbound Manager

Manage outbound links automatically: open in new tab, add nofollow, noopener, and exclude domains.

External Links in New Window / New Tab vs Cristian Outbound Manager