The use of the hashtag as a Twitter tool to denote a specific topic in order for the masses to follow along—which was first suggested (in a Tweet, naturally) by Silicon Valley regular and early adopter Chris Messina—turned 15 years old in August 2022.
If Twitte rhad it's own way, it would never have come into being on their network. Imagine social media without any hashtags.
Here’s a little history on its evolution from the humble numerical sign to the social media giant it is today.
See 5 Quick Facts About the Hashtag
It's really called an octothorpe.