Twitter will be rolling out some minor changes this summer regarding links. Twitter will automatically wrapping all links using an official t.co shorter.
The size of the shortened link ID (what matters to Twitter in regards to character size) will be a predicatble 19 characters, but the link might (and often will) be an slightly longer abbreviated version of the original. The distinction here is that you will be able to see a longer URL description - and effort to prevent link spams and malware - but only 19 characters will be counted against the sender’s total.
Twitter asserted that this would have no effect on third party applications like Bit.ly or Hootsuite, both of which offer full analytics for shortened links.Source: myurow.com