Both features "sure sound like Nielsen-like rankings of what’s hot in the U.S. or the rest of the world. Turns out they’re not," says Josef Adalian. Mariam Braimah, lead product designer for the Netflix TV app, explains that the two categories are “actually personalized content that also happens to be popular.” Adalian adds: "In other words, Netflix figures out the shows you’re most likely to enjoy, and then tells you which of those titles are currently getting a bunch of streams. If you’ve watched a lot of true-crime shows, then there’s a good chance The Vanishing at the Cecil Hotel was 'trending' for you when it came out earlier this year. But if you’re super into comedies, Schitt’s Creek and New Girl are going to be popping up in that row a lot. The streamer isn’t alone in using fuzzy definitions to define popularity: Twitter has long customized its trending topics in part based on who users follow on the service."