Twitter exceeds 100 million active users

Twitter Inc., the biggest U.S. microblogging service, said it surpassed 100 million active users worldwide.

About 55 percent of active users link to the service through a mobile device, said Dick Costolo, chief executive officer of the San Francisco-based company, at a press conference. Twitter also plans to start using so-called Promoted Tweets for brands that users don’t already follow, he said.