Biz Stone, who helped launch the microblogging service in 2006, is leaving day-to-day work at the company. Although he will remain involved with Twitter, most of his time will be spent on the relaunch of the start-up where Twitter was first developed: the Obvious Corp.
The departure marks the latest shift among the executive ranks at Twitter. Jack Dorsey, who came up with the idea for the microblog, returned in March as product chief, two years after being replaced as chief executive by the third co-founder, Ev Williams. Mr. Williams stepped down as CEO in October and was replaced by current CEO Dick Costolo.