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Previously, only links that were 20 characters or greater were reformatted with t.co.
T.co is Twitter's official URL shortener, which is designed to prevent malware and phishing attacks. Unlike other URL shorteners, such as bit.ly, Twitter displays the domain name in full so users know what they're clicking on. Existing URL shorteners, such as bit.ly, will continue to function as normal, although fewer characters will be displayed.
For example, if you entered this YouTube URL:
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It would appear as a shortened version of the original URL:
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