Dive Brief:

• Twitter's CEO Dick Costolo will step down on July 1, the micro-blogging site said on Thursday. Board chairman and Co-Founder Jack Dorsey will take on the chief executive position on an interim basis. (Dorsey will also remain the CEO of Square during this time.)
• The social media network's stock has been down since April 28 when its earnings leaked, but shares jumped as much as 13% in extended trade on the news before paring back those gains. 
• Costolo, who will remain on Twitter's board, welcomed back Dorsey via a tweet, and said in a statement, "There is no one better than Jack Dorsey to lead Twitter during this transition."

Welcome back, @jack !! https://t.co/3papmyUKg0

— dick costolo (@dickc) June 11, 2015

Dive Insight:

Twitter announced the news of the C-Suite shakeup in a regulatory filing with the SEC on Thursday.

Costolo said he is "deeply confident" of the board, management team and employees in the release, as well as iterated that he looks forward to continuing to support Twitter "however I can going forward." He also expressed praise for Dorsey's ability to lead the social site, saying "he has a profound understanding of the product and Twitter's mission in the world as well as a great relationship with Twitter's leadership team."

Our CEO, @dickc, will step down as CEO, and we’ll welcome @jack as Interim CEO on July 1 #TWTRannouncement: http://t.co/q8Ygg91jzc

— Twitter (@twitter) June 11, 2015

Investors had called for a reshuffle amid sluggish growth, CNBC reports. And Seeking Alpha reports that Twitter likely used the announcement to affirm its second quarter revenue and adjusted guidance. Twitter's stock sank almost 20% after its earnings were leaked early in April; the company posted its weakest quarter yet with first quarter revenues coming in at $436 million, compared to the $456 million analysts expected. Adjusted EPS topped estimates by three cents.

The Silicon Valley-based company said it will look to fill the post from among external and internal candidates.

In separate Twitter news, the micro-blogging site also on Thursday said it is doing away with its 140-character limit for direct messages starting in July. Twitter has been adding features to improve marketers' experience using the platform, including a new ad tool, dubbed "installed app category targeting," and the launch of the Official Partner Program to offer third-party help for businesses to leverage the site for improved marketing initiatives.