A hashtag is a word or phrase preceded by a hash sign (#), used on social media[2] platforms to identify digital content on a specific topic. Originating from Twitter[6] in 2009, it has since been integrated into various languages including Japanese, Korean, Chinese, and Russian. Aside from marking keywords or topics in a tweet, hashtags have been utilized for a range of purposes from coordinating disaster relief efforts to promoting social equality and activism[7]. They have also become an effective tool in viral marketing[1] strategies and professional development. Different social media platforms like Instagram[4], Pinterest[5], and Twitter employ hashtags to boost user engagement. The NBA and corporations like McDonald’s have even incorporated them into their advertising[3] campaigns. Furthermore, hashtags have made a significant cultural impact, fueling social movements like #MeToo and even influencing genres of music. Linguists have started studying the communicative functions of hashtags and their impact on language and culture.
A hashtag is a metadata tag that is prefaced by the hash symbol, #. On social media, hashtags are used on microblogging and photo-sharing services such as X (formerly Twitter) or Tumblr as a form of user-generated tagging that enables cross-referencing of content by topic or theme. For example, a search within Instagram for the hashtag #bluesky returns all posts that have been tagged with that term. After the initial hash symbol, a hashtag may include letters, numerals, or underscores.
The use of hashtags was first proposed by American blogger and product consultant Chris Messina in a 2007 tweet. Messina made no attempt to patent the use because he felt that "they were born of the internet, and owned by no one". Hashtags became entrenched in the culture of Twitter and soon emerged across Instagram, Facebook, and YouTube. In June 2014, hashtag was added to the Oxford English Dictionary as "a word or phrase with the symbol # in front of it, used on social media websites and apps so that you can search for all messages with the same subject".