The space of social networks is improving very quickly, adapting to the needs of society. Until recently, the hashtag on social networks has been more of a tool for organizing and searching posts by topic; but today its function is expanding and deepening; new functions appear that require detailed analysis and description. Moreover, constantly evolving, the hashtag acquires the features of a self-contained text and even goes beyond social networks. In this research, the hashtag on Instagram social network was studied from a linguistic point of view, the rules of its functioning were described using examples from English and Slavic languages; the author offers a two-level classification of functions: the functions were divided into two main blocks – searching and creative ones, within each group more specific sub-functions were singled out within. We used a continuous sampling method for selecting hashtags. As a result, we researched more than 5000 hashtags extracted from posts of users living in 13 countries and writing in Russian, Belarusian, Ukrainian, Polish, Czech, English and other languages. For more detailed analysis of the research object, we used a descriptive method using the techniques of generalization, interpretation and classification, the method of linguistic comparison, contextual analysis, elements of semantic component analysis. It was concluded that some changes occurred in the priorities of the hashtag functions from primary searching function, which helps text space organization, to the creative one, which influences the author’s personality disclosure and audience-author interaction and is associated with an increasing attention to the personal brand and the personality of the author.