Jack Dorsey created the concept of Twitter’s 140-character limit around the constraints of SMS messaging.
Dorsey’s original idea centered on short status updates that could be distributed through mobile text messages. Because standard SMS messages were limited to 160 characters, Twitter reserved space for a username and related service information, producing the famous 140-character post limit.
The limit shaped Twitter’s concise writing style and helped distinguish the platform from longer-form blogging services. It also encouraged abbreviations, links, hashtags, and rapid exchanges during live events. In 2017, Twitter expanded the limit to 280 characters for most languages.
The limit is sometimes attributed solely to a technical database restriction, but its original rationale was closely tied to SMS. Dorsey proposed the core status-sharing concept, while other co-founders and early employees helped develop, test, and operate the service inside Odeo.