Jack Dorsey

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Twitter cofounder Jack Dorsey, 2018.

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Jack Dorseyis an American Web developer and entrepreneur who, with Evan Williams and Christopher Stone, cofounded (2006) the online microblogging service Twitter(now X). He also cofounded the digital payments company Square (renamed Block in 2021).

As a teenager, Dorsey created taxi-dispatching software that was adopted by taxicab companies. He attended New York University before moving (1999) to San Francisco, where he set up a company that used the Internet to handle the dispatching of couriers and emergency vehicles as well as taxis. In 2000 he first considered using text and instant messaging (based on the principles of dispatch software) as a way of keeping in touch with friends.

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March 21, 2006: “just setting up my twttr.”

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Six years later he approached Williams and Stone with his idea; together they developed a prototype of what would become the Twitter platform. On March 21, 2006, Dorsey posted the first Twitter message: “just setting up my twttr”. The service was released to the public on July 15, 2006, and quickly became a popular social networking hub as well as a mainstream form of communication. Initially, users could post messages of no more than 140 characters, although the limit was expanded to 280 in 2017.

Dorsey served as CEO until October 2008, when he became chairman of the board. In that capacity, he was involved with Twitter’s initial public offering (2013), which raised $1.8 billion.

In 2009 Dorsey cofounded and became CEO of Square, a mobile payments venture that offered devices and software to facilitate credit card transactions. It launched in 2010 and by 2012 had more than two million users. Square initially was available only in North America, but it expanded to overseas markets in 2013, when its services became available in Japan. That year Dorsey also became a member of Disney Company’s board of directors.

In October 2015 he once again became CEO at Twitter while also remaining as Square’s CEO. During his second stint with Twitter, the company faced growing criticism about its efforts to limit access to objectionable content. It drew particular ire from conservatives, especially in 2020 when Twitter permanently banned U.S. Pres. Donald Trump for tweets that were deemed to be in violation of Twitter’s policy against glorification of violence. This came amid increased calls for government regulations on social media.

In 2021 Dorsey resigned as CEO of Twitter, saying, in part, that being a “founder-led” company was “severely limiting and a single point of failure.” That same year, Square changed its corporate name to Block, although Square remained the name of its merchant payments business. Dorsey continued to lead Block, focusing increasingly on digital payments, Bitcoin, and decentralized technologies.

He also championed Bluesky, a social networking project that began within Twitter in 2019 as an effort to give users greater control over how online content is shared and moderated. The project became an independent company in 2022. Dorsey left Bluesky’s board in 2024 after criticizing the platform’s direction.

In 2025 Dorsey introduced Bitchat, a decentralized messaging app that uses Bluetooth mesh networking instead of the Internet, continuing his interest in communication tools that operate without centralized control.