section_path: Appearance and features/Trending topics
section_name: Trending topics
paragraph_text: Trending topics
  
  Twitter introduced its "trends" feature in mid-2008, an algorithmic lists of trending topics among users. A word or phrase mentioned can become "trending topic" based on an algorithm. Because a relatively small number of users can affect trending topics through a concerted campaign, the feature has been the targeted of concerted manipulation campaigns. While some campaigns are innocuous, others have promoted conspiracy theories or hoaxes, or sought to amplify extremist messages. Some featured trends are globally displayed, while others are limited to a specific country.
  
  A 2021 study by EPFL researchers found that frequent "ephemeral astroturfing " efforts targeted at Trends; from 2015 to 2019, "47% of local trends in Turkey and 20% of global trends are fake, created from scratch by bots...The fake trends discovered include phishing apps, gambling promotions, disinformation campaigns, political slogans, hate speech against vulnerable populations and even marriage proposals." The MIT Technology Review reported that, as of 2022, Twitter "sometimes manually overrides particularly objectionable trends" and, for some trends, used both algorithmic and human input to select representative tweets with context.