Steve

This plugin allows you to specify an alternative domain name to use with the built in URL shortening service.
For this to work it requires the chosen domain to be pointed / parked on the hosting account used for your blog.

Custom Shortlink Domain

Customise the domain name used to generate shortlink URLs.

florianluce

With Shortener URL Redirect, You don’t have to do anything! 
When you publish a new post, page or custom post type, a short url is generated. You can share it, and it will redirect the user to the long url page. It’s invisible to him! 
This plugin does not use any external service.
example: 
https://your-site.com/ab2CdF redirect to https://your-site.com/my-categorie/my-post-name
optimisation available:
<ul>
<li>Create a short URL for each new publication (post, custom post types, page)</li>
<li>Redirect short URL to long/default URL</li>
<li>Display the short link to copy on admin publication</li>
</ul>
Notes: 
This plugin is actually not tested with: 
* Multisite network 
* Translate plugins 
* Other plugins

Shortener URL Redirect

Generate short url for all posts, custom post types and pages to redirect your user to the long URL. No more long URLs share!

Custom Shortlink Domain vs Shortener URL Redirect