Dick Costolo is stepping down as the CEO of Twitter

Dick Costolo, Twitter’s embattled chief executive, is stepping down, the company said Thursday. Jack Dorsey, the company’s co-founder and chairman, will serve as interim chief executive while the board searches for a permanent successor. The change is effective July 1. Twitter shares were up more than 7 percent in after-hours trading immediately after the news was announced. Since Twitter’s debut as a public company in 2013, Mr. Costolo has repeatedly disappointed Wall Street as the company struggled to attract new users, refine its products and develop new forms of advertising. Mr. Costolo’s departure is likely to renew speculation that Twitter is an acquisition target for the handful of tech giants that could afford the company, which currently has a market valuation topping $24 billion. In recent weeks, Google has been rumored to be eyeing Twitter, but people familiar with the companies denied that a deal was in the works.