thearchivist.funA user proposes the Twitter hashtag
On August 23, 2007, Chris Messina used a hashtag proposal to group related Twitter messages through a shared textual marker.
Context and provenance
Twitter co-founder Biz Stone's tenth-anniversary account describes Chris Messina suggesting the hash character as a way to group related messages. Messina then used the idea in a tweet on August 23, 2007, and the practice spread before Twitter later made hashtags clickable. This history should be read specifically as the Twitter hashtag's emergence, not the invention of the hash symbol or every earlier use of it. Its significance lies in a user convention becoming a supported feature. People were already organizing conversation through their own behavior; the platform subsequently formalized a way to follow it. The visible marker connected individual messages without requiring their authors to belong to one predefined group.
Why it matters
Hashtags show users helping design a platform through repeated practice. A small convention can become infrastructure for discovery, collective attention, and conversation when software begins to support it.