Twitter's url shortner t.co
Old news. Twitter is now using “t.co” to shorten url posted thru twitter.com. However, url will be displayed as the original following ellipsis.
For example, go to this page: http://xahlee.org/sl/lsl-script_count.html, click on the tweet button. Then, twitter generates a link like this 〔http://t.co/BAPV0SJ9〕, but when viewed in twitter.com, it is displayed as 〔xahlee.org/sl/lsl-script_…〕. And when you copy the text, the shortened url is copied.
According to twitter, quote:
Twitter's link service (http://t.co) is used on all links included in Direct Message notification emails …
If you just use twitter.com to post a normal tweet, it's not shorterned. For example, if you post 〔http://google.com/〕 or〔http://xahlee.org/Periodic_dosage_dir/skami_prosa.html〕 it'll come out as is.