Embattled Twitter CEO Dick Costolo is resigning

Dick Costolo, Twitter’s embattled chief executive, is stepping down, the company said.

Jack Dorsey, the company’s co-founder and chairman, will serve as interim chief executive while the board searches for a successor.

The change is effective July 1.

Since Twitter’s debut as a public company in 2013, Costolo has repeatedly disappointed Wall Street as the company struggled to attract new users, refine its products and develop new forms of advertising.

The analyst firm eMarketer estimates that Twitter’s monthly user base will grow 14.1 percent this year, down from 30 percent two years ago.

Twitter accounted for 3.6 percent of the $19.2 billion mobile Internet ad market in the United States last year, according to eMarketer, while Facebook held an 18.5 percent share and Google dominated with 36.9 percent.

“I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the company,” Costolo said in a statement.

Pressure on Costolo grew in recent weeks after Chris Sacca, an early Twitter investor, went public with an 8,500-word analysis of what Twitter could be and how it could get there. Shortly after the essay was published on Sacca’s blog, Costolo fielded some tough questions from Twitter stockholders at the company’s annual shareholder meeting.

Sacca’s manifesto calls for a much deeper rethinking of Twitter’s service, which is still focused on 140-character text messages, to attract new users beyond the 302 million active users it reported for the first quarter.

“Twitter can afford to build the wrong things,” Sacca wrote. “However, Twitter cannot afford to build the right things too slowly.”

Twitter said its second-quarter financial results were on track to meet its prior forecasts.

This story was originally published June 11, 2015 at 6:11 PM with the headline "Embattled Twitter CEO Dick Costolo is resigning."