American computer programmer and entrepreneur widely known as a co-founder and CEO of Twitter, and as the founder and CEO of Square, a mobile payments company. In 2008, he was named to the MIT Technology Review TR35 as one of the top 35 innovators in the world under the age of 35. For 2012, The Wall Street Journal gave him the “Innovator of the Year Award” for technology.
Evan Williams, Biz Stone and Noah Glass co-founded Obvious Corporation, which then spun off Twitter Inc. with Dorsey as the CEO in 2006. As chief executive officer, Dorsey saw the startup through two rounds of funding by the venture capitalists who backed the company. He reportedly lost his position for leaving work early to enjoy other pursuits such as yoga and fashion design.
As the service began to grow in popularity, Dorsey chose the improvement of uptime as top priority, even over creating revenue – which, as of 2008, Twitter was not designed to earn. Dorsey described the commercial use of Twitter and its API as two things that could lead to paid features. He describes his three guiding principles, which he says are shared by the company, as simplicity, constraint and craftsmanship.
On 16 October 2008, Williams took over the role of CEO, while Dorsey became chairman of the board.
On 28 March 2011, Dorsey returned to Twitter as Executive Chairman after Dick Costolo replaced Williams as the CEO. On 10 June 2015, Costolo announced that he was resigning as CEO of Twitter effective 1 July 2015. Dorsey would assume the post of Interim CEO upon Costolo’s departure. He was named permanent CEO of Twitter on 5 October 2015. On the day after the controversy about Twitter’s new algorithms for tweets, Dorsey responded to the trend saying it was only a hoax.
In May 2016, Dorsey announced that Twitter would not count photos and links in the 140-character limit to free up more space for text. This move was an attempt to entice new users since the number of tweets per day was at an all-time low of about 300 million in January 2016 compared to about 500 million in September 2013 and its peak of 661 million in August 2014.

Link to Wikipedia biography