The objectives of the thesis is to discriminate the impact of active polarization in online social networks, i.e. the presence of antagonist communities, and to characterise its dynamics in time. We focus on the social network X/Twitter and, precisely, on the Italian political and journalistic debate in the years 2018 to 2022. The two main actions that users on X/Twitter can adopt to publicly express their consent or dissent are retweets and quotes: when retweeting a user shares a tweet on their profile, while when quoting the user shares a tweet and adds a public text on it. To construct our dataset, we select all the tweets made by a selected sample of accounts that we refer to as leaders.