The default WordPress “shortlink” URLs look like this: <code>http://www.example.com/blog/?p=123</code>, where “<code>123</code>” is actually a 7+ digit decimal number. This plugin shrinks your shortlinks by encoding that number into only 4 characters, and using the abbreviated URL prefix of your choice.
On my site, the default shortlinks are 35 bytes long, even though I have a very short domain name. This plugin shrinks them to 21 total bytes, which is comparable to most public URL-shortener services, and better than many.
E.g., this: <code>http://www.jwz.org/blog/?p=13240780</code> 
becomes: <code>http://jwz.org/b/ygnM</code>
This doesn’t affect your (long) permalinks: those can still be in whatever format you like.

Base64 Shortlinks

This plugin makes your shortlinks shorter!

Gerald Drißner

kURL connects your WordPress site to your self-hosted YOURLS installation.
The name kURL combines kurz URL — “short URL” in German — with the familiar term URL. In other words, kURL is built for creating and managing short URLs from WordPress.
It lets you create short URLs for posts, pages, and supported custom post types directly from the WordPress admin area. You can generate links manually, create them automatically when content is published, assign custom keywords, refresh click statistics, and process older content in bulk.
kURL also includes migration tools for older Better YOURLS data, local logging for troubleshooting, and optional helper code for true remote deletion and safe reverse lookup on the YOURLS side.
Requires a self-hosted YOURLS installation with API access. No third-party shortening service is included.
If your server uses Nginx instead of Apache, add a deny rule for the <code>wp-content/uploads/kurl/</code> directory in your Nginx configuration to protect the log folder.
<h4>Features</h4>
<ul>
<li>Create short URLs from the WordPress editor.</li>
<li>Automatically create short URLs when content is published.</li>
<li>Use custom keywords when creating short URLs.</li>
<li>Generate short URLs manually for any target URL from the dashboard.</li>
<li>Refresh and store click statistics from YOURLS.</li>
<li>View saved links, latest links, top links, and recent YOURLS activity in the dashboard.</li>
<li>Bulk-generate short URLs for existing content in AJAX batches.</li>
<li>Import legacy data from the Better YOURLS plugin.</li>
<li>Optional YOURLS helper extension for remote deletion and safe long-URL lookup.</li>
<li>Activity and error logging for troubleshooting.</li>
<li>Optional short URL column in WordPress content list screens.</li>
<li>Experimental sync and cleanup tools.</li>
</ul>
<h3>Credits</h3>
French translation: Norbert Jung.

kURL – Short URL Manager for YOURLS

Connect WordPress to a self-hosted YOURLS instance to create, sync, manage, and track short URLs from the admin area.

Base64 Shortlinks vs kURL – Short URL Manager for YOURLS