Twitter rejected the hashtag — users invented it anyway

In August 2007, product design consultant Chris Messina proposed a simple idea: use the # symbol to group conversations on Twitter. He tweeted, 'how do you feel about using # (pound) for groups. As in #barcamp [msg]?' Twitter did not adopt the proposal. The company had no plans to build the feature, and the convention was left unowned by the platform.

Users adopted the hashtag organically. In October 2007, during the San Diego forest fires, users coordinated information with the #sandiegofire hashtag. The practice spread internationally during the 2009 Iranian election protests, where users employed both English and Persian hashtags to share news. The convention worked without any official support from Twitter — it was a user-created system that the platform had not built.

Twitter finally began hyperlinking hashtags on July 2, 2009, nearly two years after Messina's proposal. The company introduced Trending Topics in 2010, making hashtags a central part of the platform. The hashtag had become the defining feature of Twitter — the primary way users discovered conversations, organized events, and tracked breaking news. Other platforms including Instagram, Facebook, and YouTube later adopted the format.

Messina never patented the idea, stating that hashtags 'were born of the internet, and owned by no one.' Twitter's failure to recognize the value of the feature early meant that the platform's most important tool was invented by its own users. The company that built the infrastructure did not build the feature that made it work.