Who is credited with inventing the hashtag on Twitter?

Chris Messina is credited with inventing the hashtag as a social-media tagging system on Twitter. In 2007, the American blogger and product consultant proposed using the hash symbol to group messages about shared topics, events, and conversations.

Messina drew inspiration from Internet Relay Chat, or IRC, where a hash symbol had already been used to identify channels and discussion groups. His proposal adapted that idea to Twitter, allowing users to attach informal metadata to short posts. A search for the same tagged word could then bring related messages together without requiring a formal database category.

Twitter initially showed little enthusiasm, but hashtags became more useful during events such as the 2007 San Diego County wildfires, when users used tags to track updates. The practice spread widely and was eventually adopted by platforms including Instagram, Facebook, YouTube, and TikTok.

Messina is sometimes described as the inventor of the hashtag, but more precisely, he proposed its modern social-media use. The # symbol itself is much older, with established roles in publishing, programming, telephony, and online chat.