Sometimes, web posting limits people to a certain number of characters therefore they need to reduce the length of their links using URL shorteners.
These applications are specialized software applications that enable users to apply an HTTP redirect to a specific domain name, thus linking a short link to stand for a long one.
The main purpose for this technique is posting on Twitter, which imposes a limit of 140 characters for all messages, however this is not the only functionality for these utilities.
Besides being standalone apps, URL shorteners can also be browser add-ons meant to reduce the time spent for finding the right tool for cutting the length of a web address.