Twitter co-founder Jack Dorsey, who served as the company's original CEO and has since gone on to co-found e-commerce start-up Square, will be returning to a day-to-day role at the company as "executive chairman." The move was formally announced in a tweet by Twitter CEO Dick Costolo this morning.
"Excited that Twitter Chairman @jack will be returning to the company day-to-day leading product as Executive Chairman," Costolo's tweet read.
Dorsey came up with the original concept for Twitter--something that has been very noticeable in the company's recent fifth-birthday commemorations--and served as CEO until 2008 when after a well-reported ouster he was replaced by fellow co-founder Evan Williams. Dorsey remained Twitter chairman, but in the meantime co-founded Square, which uses a piece of hardware to turn mobile devices into credit card readers, and became one of the tech entrepreneurship world's more prominent angel investors.
Late last year, Evan Williams stepped down from the Twitter CEO post and was replaced by Costolo, a former Googler who had been serving as chief operating officer. Williams remains in a product strategy role, but according to reports has been a less and less prominent figure in the company's quotidian operations.
Dorsey will be returning to a dramatically different Twitter. Earlier this month, Twitter released a set of numbers that says 140 million tweets are posted every day, and that the company now has 400 employees. It also has revenue strategies in place, something that it most certainly didn't back when Dorsey was CEO the first time around, but its business model remains experimental.
In a tweet, Dorsey said that he would keep "leading Square forevermore as CEO," but he does have some help now: in August, the company hired PayPal veteran Keith Rabois as general manager.
This post was last updated at 9:52 a.m. PT.