Now sharing links on Twitter.com is more simple and instant. Twitter has rolled out automatic URL shortening feature. As soon as you paste a link and press Tweet button, the URL will be shorten automatically that only takes up 19 characters.
In addition, users will be able to see the original link to know which website the link points to. The feature also enhances security measures; if users click links that are reported as malicious, he/she will be directed to a warning page.
NOTE: You can continue to use your favorite third-party link shortening services.
Source: Twiiter Blog