Erick Hitter

WordPress 3.0 introduced a native shortlinks feature, which builds URLs using query strings. This plugin converts those URLs to ones using pretty permalinks, which makes for a nicer-looking URL and improves shortlinks’ ability to be cached.
Posts and pages are supported by default, while filters make it possible to support other post types.
For example, https://example.com/?p=123 becomes https://example.com/p/123/.

ETH Simple Shortlinks

Convert WordPress's query-based shortlinks to pretty permalinks that are cacheable. https://example.com/?p=123 becomes https://example.com/p/123/.

Ryan Street

Jason Grim

Background
WordPress has created the wonderful functionality of generating shortlinks for post on your blogs. With advanced 
permalink structures a single link to your site can take up 89% of a short email or a facebok update. However, 
Wordpress created a very ugly system, the shortlink system simply provides the default permalink structure with ugly 
url variables.
Here is the documentation on adding shortlinks to your themes on the <a href="https://codex.wordpress.org/Function_Reference/the_shortlink" title="Wordpress.org - Shortlinks" rel="nofollow ugc">WordPress Codex</a>
Use
Some themes use the template method to share the short url of your post. The use of this plugin would convert all of those 
links to trackable ones with bit.ly or shorter ones with the other services.
Also, when you create a new post a button is created next the the URL of your new post. If you click the “Get Shortlink” button 
a popup will provide a simple little link to share with all of your friends and fans.

Generate Shortlinks

Uses bit.ly, Ur.ly, and Is.gd to create handy shortlinks to share your WordPress Posts quickly and easily!

ETH Simple Shortlinks vs Generate Shortlinks