Jack Dorsey is back in charge of Twitter

Jack Dorsey has announced that he is re-taking the reins of the social network that he helped build. Dorsey had been the interim CEO since it was announced that previous CEO Dick Costolo was stepping down in June of this year. Twitter created a search committee after Costolo's departure that included former Twitter CEO, Evan Williams, to find a new boss. Turns out that the figure was there, all the time. In addition, Dorsey will remain as CEO of Square, the mobile-payments firm he founded when he left Twitter. This will be Dorsey's second term as CEO, the first abruptly ending in 2008 when he was replaced as CEO by Ev Williams.

Dorsey will have his hands full as the company struggles to grow its active user base. During its last quarterly results, Dorsey noted that the company needs to do a better job explaining what Twitter actually does. It's been exploring ways keep new users engaged. These include experimenting with surfacing trending news items and buy buttons. As he explains in his 140-character missive, Dorsey will be the CEO of both Twitter and Square, with Adam Bain, Twitter's current head of revenue and partnerships becoming the social network's COO. At the same time, former CEO Dick Costolo has resigned from Twitter's board and is no longer with the company.

If Dorsey can figure out how to get new users to stay with the service is yet to be determined. What is certain is that the market thinks his new job as CEO is a good idea. The company's stock jumped over five percent earlier today when Recode broke the story that Twitter would name Dorsey as it's new CEO before the official announcement.

[Image credit: AFP PHOTO / JUSTIN TALLIS]