Jack Dorsey Back At Twitter; Ev Williams “Less Involved,” Company Says

More changes today atop the perch at Twitter: Jack Dorsey, the company co-founder who famously sent the first tweet five years ago, is back in a day-to-day role as Executive Chairman and will be in charge of the Twitter product. Evan Williams, meanwhile, is “less involved day-to-day” at Twitter, the company tells us.

Appropriately, Twitter CEO Dick Costolo announced Dorsey’s return via tweet today. Dorsey followed it up with confirmation of the new move, and confirmed that he’ll also remain the CEO at mobile payment provider, Square.

Here’s the text of Dorsey’s tweet:

Today I’m thrilled to get back to work at @Twitter leading product as Executive Chairman. And yes: leading @Square forevermore as CEO. #200%

Of course, it was just a few months ago that co-founder Evan Williams stepped down as CEO with the promise that he would be “completely focused on product strategy.” But there’ve been reports in recent weeks that Williams no longer works much at Twitter HQ, and the company confirmed that via email this afternoon:

Ev … decided a couple months ago to be less involved day-to-day at Twitter. Ev continues to have a close relationship with the company providing strategic advice and, of course, he remains an active board member.

With Dorsey moving from the Twitter board to lead product and Ev doing the opposite, the two have essentially switched positions.

Postscript: Williams has talked about his lessened involvement at Twitter in a blog post that says his “mind started to wander” after he stepped down as the company’s CEO last year.