Breaking: Twitter CEO Evan Williams Steps Down, COO Dick Costolo Steps In

Dick Costolo, the company's COO — who appeared in late September at TheWrap's Grill conference — will replace him

Twitter chief executive Evan Williams announced on Monday that he is stepping down as CEO.

Williams will be replaced by chief operating officer Dick Costolo, who joined Twitter last year and spoke Sept. 22 at TheGrill, the inaugural media and entertainment industry conference hosted by TheWrap.

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Williams said he is stepping down to "become completely focused on product strategy."

The move was not unexpected. Costolo has been viewed as a better fit for Twitter's CEO slot within the tech community — now that the company is looking to capitalize on its explosive growth. And many Silicon Valley watchers were beginning to question whether or not Twitter — despite the buzz — has a real strategy for generating revenue.

Costolo, an early investor in Twitter, founded Feedburner, the RSS reader that he sold to Google in 2007 for a reported $100 million.

And Costolo has become a prominent presence at Twitter — at least as prominent as Williams, if not more — when it comes to explaining new products to the advertising and investment communities.

Just last week, Costolo was in New York to talk about Twitter's Promoted Tweets feature.

“We’re definitely beyond the experimentation stage,” Costolo told the audience at Mixx, a conference hosted by the Interactive Advertising Bureau. “We feel like we’ve cracked the code on a new kind of advertising — advertising that starts out as organic content.”

Williams had long preached that the company was interested in growing without worrying about making money.

"If we spent time monetizing early on," Williams told the New York Times in 2008, when he took over for Jack Dorsey, Twitter's original, "it would have meant we weren’t doing other things that made the product better for users.” Dorsey is now chairman of Twitter.

Here's Williams' greater-than-140-character announcement:

By all accounts Twitter is on a roll. We've redesigned our web site to great user feedback. Our user and usage numbers are growing at a rapid clip all around the world. We’ve launched an early, but successful, monetization effort. And, many top engineers, product designers, sales people and other key folks have joined our quickly growing team.

In fact, there are 300 people working at Twitter today—compared to about 20 when I took the CEO job two years ago. Back then, people were creating about 1.25 million tweets a day—compared to 90 million today. In those same two years, we grew from 3 million registered users to more than 160 million today.

The challenges of growing an organization so quickly are numerous. Growing big is not success, in itself. Success to us means meeting our potential as a profitable company that can retain its culture and user focus while having a positive impact on the world. This is no small task. I frequently reflect on the type of focus that is required from everyone at Twitter to get us there.

This led to a realization as we launched the new Twitter. I am most satisfied while pushing product direction. Building things is my passion, and I’ve never been more excited or optimistic about what we have to build.

This is why I have decided to ask our COO, Dick Costolo, to become Twitter’s CEO. Starting today, I’ll be completely focused on product strategy.

When I insisted on bringing Dick into the COO role a year ago, I got a lot of questions from my board. But I knew Dick would be a strong complement to me, and this has proven to be the case. During his year at Twitter, he has been a critical leader in devising and executing our revenue efforts, while simultaneously and effectively making the trains run on time in the office. Dick can be even more effective at this now because Ali Rowghani, Adam Bain, Mike Abbott, Katie Stanton and Kevin Thau joined our leadership team this year and are having a big impact. Given Dick’s track record as a three-time successful CEO, I’m confident we can make this a smooth transition.

I’m extremely proud of how far Twitter has come in the last two years. And, I couldn’t be more excited about where our amazing team will take it next.