A hashtag is a metadata tag operator that is prefaced by the hash symbol ,. On social media , hashtags are used on microblogging and photo-sharing servicesβespecially Twitter and Tumblr βas a form of user-generated tagging that enables cross-referencing of content by topic or theme.
After the initial hash symbol, a hashtag may include letters, numerals or other punctuation. The use of hashtags was first proposed by American blogger and product consultant Chris Messina in a tweet. The number sign or hash symbol , , has long been used in information technology to highlight specific pieces of text.
In , the number sign was used to denote immediate address mode in the assembly language of the PDP [ 12 ] when placed next to a symbol or a number, and around , ' ' was introduced in the C programming language to indicate special keywords that the C preprocessor had to process first.
The use of the pound sign in IRC inspired [ 16 ] Chris Messina to propose a similar system on Twitter to tag topics of interest on the microblogging network. According to Messina, he suggested use of the hashtag to make it easy for lay users without specialized knowledge of search protocols to find specific relevant content. Therefore, the hashtag "was created organically by Twitter users as a way to categorize messages". Messina's suggestion to use the hashtag was not immediately adopted by Twitter, but the convention gained popular acceptance when hashtags were used in tweets relating to the San Diego forest fires in Southern California.
Hashtags have since played critical roles in recent social movements such as jesuischarlie , BLM , [ 23 ] and MeToo. Beginning July 2, , [ 26 ] Twitter began to hyperlink all hashtags in tweets to Twitter search results for the hashtagged word and for the standard spelling of commonly misspelled words.
