Who proposed using the hashtag symbol for topics on Twitter in 2007?

Chris Messina proposed using the hashtag symbol for topics on Twitter in 2007.

Messina, a technology expert and open-source advocate, suggested grouping conversations with the pound sign in an August 2007 blog post. He also posted an early public proposal on Twitter, asking what people thought about using “#” for groups. The idea drew inspiration from Internet Relay Chat, where symbols helped organize channels.

Twitter did not immediately introduce hashtags as a formal product feature. Users adopted the convention organically, and the company eventually made hashtags clickable and searchable. This transformed the symbol from a niche organizational mark into a standard tool for tracking events, movements, television programs and breaking news.

A hashtag consists of the hash symbol followed by a word or phrase without spaces. It is not the same as a mention, which uses the @ symbol to identify an account. Hashtags later spread far beyond Twitter to Instagram, Facebook, TikTok and other platforms.