URL Shorteners (or URL Shortening services) have been of immense benefit to the online world. Posting long, unwieldy URLs was awkward especially when you want to post it on sites that limit character counts like some social media sites. Also, when all you want is an easy-to-remember URL. That's why these services still persist to this day.
But there is one huge problem when it comes to them: Link Rot. So what is Link Rot? Let's assumme you are the owner of a teeny-tiny website somewhere in cyberspace. You post a link to one of your blog posts on a forum you frequent: http://my.website.com/path/to-blog-post. It works! People are clicking it to your website. But then suddenly you feel that your teeny-tiny website needs to be on a better domain: http://my.hotwebsite.com. You choose to migrate it to this new domain. Or, God forbid, you get tired of it all and let your hosting to lapse or you just pull down the entire thing. Now, what happens to your previous http://my.website.com/path/to-blog-post URL that you posted on the forum? It stops working. That is what is called "Link Rot". Your previous URL's that you posted all over the internet stop working.
This is what afflicts much of the URL shortening world. A good URL shortener pops up. People use it to create short links that they post all over. Then, one day the service dies and all the links that pointed to it stop redirecting.
How do you mitigate this? This is blog post for another day.
See you next time!