Ruby on Rails was used to build Twitter. It is a specialized Web-application framework for the Rubycomputer programming language. Its interface allows open adaptation and integration with other online services. The service was designed in 2006 by Evan Williams and Biz Stone, each of whom worked at Google before leaving to launch the podcasting venture Odeo. Williams, who had previously created the popular Web authoring tool Blogger, began experimenting with one of Odeo’s side projects—a short message service (SMS) then called Twttr.

Seeing a future for the product, Williams bought out Odeo and started Obvious Corp. to further develop it. Engineer Jack Dorsey joined the management team, and the completed version of Twitter debuted at the South by Southwest music conference in Austin, Texas, in March 2007. The following month Twitter, Inc., was created as a corporate entity, thanks to an infusion of venture capital.

In the beginning, Twitter was primarily a free SMS with a social networking element. As such, it lacked the clear revenue stream that one could find on sites that derived income from banner advertising or membership fees. With the number of unique visitors increasing some 1,300 percent in 2009, it was obvious that Twitter was more than a niche curiosity. However, in a year that saw the social networking juggernaut Facebook turn a profit for only the first time, it was not clear whether Twitter could achieve financial independence from its venture capital investors. In April 2010 Twitter unveiled “Promoted Tweets”—advertisements that would appear in search results—as its intended primary revenue source.