A hashtag is a metadata tag with the sign # it. On social media, hashtags are used for microblogging and photo-sharing services such as Twitter or Instagram as user-generated tagging that enables cross-referencing of content by topic or topic. For example, a search for the hashtag #love within Instagram returns all posts that have been tagged with that term.
The use of the hashtag was first proposed by American blogger and product consultant Chris Messina in a 2007 tweet. Messina made no attempt to patent the uses as he felt "they were born of the Internet and were not owned by anyone". Hashtags became entrenched in the culture of Twitter and soon emerged on Instagram, Facebook, and YouTube.