Key figures: Jack Dorsey, Evan Williams, Biz Stone, Noah Glass (co-founders)
Summary
Twitter, the microblogging and social-networking service, was launched publicly on July 15, 2006. It grew out of the San Francisco podcasting company Odeo, founded by Evan Williams and Noah Glass, whose core business had been undermined when Apple integrated podcasts into iTunes in June 2005. During a brainstorming session in a San Francisco playground on March 21, 2006, Odeo engineer Jack Dorsey proposed a service that would let an individual send a short status update by SMS to a small group of people. The first message — “just setting up my twttr” — was posted by Dorsey that same day, several months before the public launch.
Posts were capped at 140 characters, a limit derived from the 160-character maximum of SMS messages (leaving room for a username), which became one of the platform’s most debated and defining constraints. The character limit remained at 140 until November 7, 2017, when Twitter doubled it to 280.
Founding Context: Odeo’s Failure and the Pivot
Odeo’s Disruption
Odeo had been founded in 2004 by Noah Glass and Evan Williams, with Williams bringing experience and capital from his earlier success selling Blogger to Google in 2003. The company attracted seed funding and a small team, including Biz Stone and Jack Dorsey, to build a podcasting platform. Apple’s announcement at the Worldwide Developers Conference on June 6, 2005 that iTunes would natively support podcast subscription effectively destroyed Odeo’s business model overnight: a direct distribution channel that Apple controlled for free made Odeo redundant before it could scale.
The company’s response was a company-wide “hackathon” style exploration of alternative ideas. Dorsey’s proposal built on an idea he had developed since age 15 about dispatch systems and real-time status updates — he wanted a system that let you know what your friends were doing at any given moment, similar to the Away Messages on AIM (AOL Instant Messenger) but broadcast publicly. The working prototype was built in roughly two weeks by Dorsey, Stone, Glass, and engineer Florian Weber.
The First Tweets
The internal prototype launched within Odeo on March 21, 2006, and the company spent the following weeks using the service exclusively among themselves. Evan Williams sent the second ever tweet: “inviting coworkers to [Odeo],” following Dorsey’s first. Noah Glass was an early enthusiast, christening the service “Twitter” (derived from “twit” and “twitter,” meaning a short burst of information) after the team rejected alternatives including “Twitch.”
Technical Architecture and Design Choices
The SMS Foundation
Twitter’s architecture in 2006 was built primarily around SMS (Short Message Service), reflecting the pre-smartphone era. Users sent tweets by texting the short code 40404 from their mobile phones — a system that required no smartphone or mobile internet connection. The 140-character limit was a direct consequence of this SMS-first design, as SMS messages are limited to 160 characters; 140 characters for content and 20 reserved for the username prefix.
This design choice made Twitter genuinely accessible in 2006 when smartphone penetration was minimal and mobile internet was slow and expensive. It also meant Twitter worked on virtually every mobile phone sold — the service was agnostic to handset capability in a way that smartphone-only apps were not.
Early Feature Set
The July 2006 public launch was extremely minimal: users could post tweets (then called “updates”), follow other users, and receive updates on their mobile phones or a simple web interface. There were no retweets (a user-invented convention that Twitter eventually formalised), no hashtags (introduced by user Chris Messina in August 2007), no @-reply conventions (also user-invented), and no API. The character limit was the only significant constraint on the content of posts.
The SXSW Breakthrough
Adoption was modest through 2006 — the service had roughly 50,000 users by the end of 2006. The turning point came at the South by Southwest (SXSW) interactive festival in Austin, Texas, in March 2007, where Twitter deployed an unusual promotional tactic: the company arranged for a 60-inch plasma screen to display real-time tweets in the hallways of the convention center, making the service visible as a live ambient feed to thousands of conference attendees simultaneously. Daily tweet volume jumped from approximately 20,000 per day before SXSW to 60,000 per day during the festival — a tripling in one week that gave the service its first viral moment.
Twitter won the SXSW Web Award in the blog category, and the combination of award recognition and the hallway plasma screens created a self-reinforcing adoption loop among the tech-industry early adopters who attended the conference and who would go on to evangelise the service online.
Significance
Twitter’s 2006 launch introduced and popularised the “microblog” — a feed of very short, public, real-time messages — and helped define the participatory, user-generated character of the Web 2.0 era that Time magazine recognised later in 2006 by naming “You” its Person of the Year. The platform’s brevity, public-by-default design, and SMS accessibility gave it a distinct identity from the longer-form blogging and social networking of the era.
In subsequent years Twitter became a central venue for breaking news — from the 2009 Hudson River plane landing (tweeted before major news outlets reported it) to the Arab Spring uprisings (2010–2012), where the platform served as an organizing tool — demonstrating how a small side project conceived within a failing startup could grow into globally significant communications infrastructure. Twitter went public in 2013 with a market capitalisation of approximately $24 billion; the company was acquired by Elon Musk for $44 billion and rebranded as “X” in 2023, but the service traces its origin to the July 2006 launch and the March 2006 brainstorm among Odeo’s staff.
Sources
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[Twitter launches July 15, 2006 — HISTORY](https://www.history.com/this-day-in-history/July-15/twitter-launches) - History of Twitter — Wikipedia