I have seen many (and also used some) sites offering the web service that provides short aliases for redirection of long URLs. They mostly use very short domain with a short top level domain of a country, like .ly of Libya and .in of India.
TinyURL, bit.ly, shorl, doiop, and lnk.in are some of them. These services provide us an easy way to share the links, when the space is limited. I have used tinyurl service to send urls to friends in SMS and in the profiles where space is limited.
t.co
"Twitter uses the t.co domain as part of a service to protect users from harmful activity, to provide value for the developer ecosystem, and as a quality signal for surfacing relevant, interesting Tweets."
Here, t.co is a url shortener that is used by twitter by default, such that whenever we post a url, it is shortened by this service. This ensures that our tweets with urls fit into the 140 character limit. Since t.co is part of twitter and is not open for the public to shorten their links, no one can customize their shortened url's, unlike some other services like bit.ly. This might be a minus point, as it prevents the possibility of having descriptive urls such as http://t.co/mobileplatform, forcing everyone to use what is provided by default, like http://t.co/V99uVV3K. This also eliminates the misleading urls. For instance, http://t.co/mobileplatform needless to be a page on mobile platform at all.
Funky one. Comes with ads, letting you earn a few bucks while using this service. But I personally do not like this one for professional uses. Who needs a few cents, than providing the users with the content immediately? Reader satisfaction is more important. Why waste their 10 seconds with advertisements? Mostly they won't click the link at all. Some of the advertisements often include broken links too, which I faced recently, also providing a never ending loop. So nothing earned either. Loss-loss deal. For personal or enterprise uses, I don't recommend displaying an advertisement before the content, unless advertisement is your major revenue, than the actual content provided.
bit.ly
Bit.ly provides the option to register an account and keep track of the url history for the user, providing options to track and monitor the clicks. It also lets us customize the url, instead of providing default random urls with meaningless text like http://bit.ly/V99uVV3K.
I was just impressed by the way bit.ly redirects when a wrong url is entered.
Page Not Found
Uh oh, bit.ly couldn't find a link for the bit.ly URL you clicked.
Maybe one of the pufferfish ate it, or maybe there are some extra characters on the end of the URL.
Most bit.ly URLs are 4-6 characters, and only include letters and numbers. Manage your URLs
When I see something weird or meaningless text following a web url, I simply get to know that those will redirect me to somewhere else. There is a nice option in many of these services, where we are allowed to choose our own name to be appended, thus providing an option to choose meaningful names.
Till very recently I haven't seen the other side of these services, other than the links those redirect us to personal blogs. I had to think much on this when I received spams with messages such as "Really Interesting! Wanna have a look!!", with shorter urls, which direct us to shock sites. For these reasons, some social networking sites including facebook have banned the usage of some of these services.
Yes, I know we have the preview option before literally going to the site. But in reality, how many of us are ready to spend time on this?