Who introduced the use of hashtags on Twitter in 2007?

Chris Messina introduced the use of hashtags on Twitter in 2007.

On August 23, 2007, product designer and blogger Chris Messina proposed using the pound sign to group related Twitter conversations. His idea was influenced by Internet Relay Chat, where the same symbol identified channels and topics. The proposed format gave users a lightweight way to label messages without requiring a formal classification system.

Twitter did not immediately adopt the idea as an official feature. Users nevertheless began using hashtags, and the practice became especially visible during the 2007 San Diego County forest fires, when tags helped people follow updates about the disaster. Hashtags later spread to services including Instagram, Facebook, YouTube, and Reddit.

Messina proposed the system, but its success was a community-driven development rather than a feature launched by Twitter’s founders. That distinction explains why answers such as Evan Williams, Biz Stone, or Noah Glass are not the canonical answer. Twitter eventually made hashtags clickable in 2009 and added hashtag-based trending topics in 2010.