Jack Dorsey, Evan Williams, and Biz Stone founded Twitter, the short-message social network now associated with the brand X.
Twitter grew out of an idea for a mobile status-updating service developed at Odeo, a podcasting company. Dorsey proposed the short-message concept, and the first tweet was sent on March 21, 2006. The service was initially known as twttr before adopting the Twitter name and becoming a standalone company.
Noah Glass was also an important early co-founder and helped shape the Twitter name, so fuller historical lists often identify four co-founders: Dorsey, Williams, Stone, and Glass. That does not make the stored answer unfair; Dorsey, Williams, and Stone are all widely recognized as Twitter founders.
Twitter became known for public, chronological-style short posts, hashtags, replies, and rapid real-time discussion. A common mix-up is confusing it with Facebook or Instagram, which are separate platforms. After Elon Musk’s acquisition, Twitter was rebranded as X in 2023.