The Netflix algorithm

How Netflix recommendations keep you hooked

How do you choose what to watch on Netflix? Recommendations from other people? Did you read about a show online? See an ad? Or, did it pop up on your Netflix homepage?

Over 100 million people worldwide use the platform, and up to five profiles can be created per account. From these user profiles, Netflix can see what that person is watching, what they watched before that, what they go on to watch, how long they watch it for, what devices they watch it on and even what time of day they watched it. This data is broken down into two types: explicit and implicit. Explicit data is what you literally tell Netflix, like giving a show a thumbs up. Implicit data is made up of what you don’t explicitly tell Netflix. If you watch an entire series in two days or stopped watching after ten minutes, you don’t need to give it a thumbs up or down for Netflix to get the message.

Netflix staff watch all the shows available on the site and tag them based on their content, genre and mood, such as “Absurd TV Comedies” or “Binge-worthy TV Thrillers”. You may remember choosing a few shows or films you already liked when you created your Netflix profile. Netflix uses these to start tuning your recommendations from the start. There are also over two thousand ‘taste groups’ Netflix places users into, and then only suggests shows which users in your group enjoyed.

Another subliminal trick Netflix uses is to do with the picture that is shown with each new show or movie. Netflix also changes this based on the user’s watch history. So, if you watch a lot of rom-coms, the picture shown with a given show might be of two characters kissing, even if that doesn’t accurately portray the show’s story. This picture could also change as the system ‘learns’ more about you and other users. So, for any given show, there could be many possible images ready, all ranked based on context and taste profile. For someone who likes horror films, a picture of two people kissing might be ranked lower than for someone Netflix has decided prefers romances.

Which would be a little bit creepy if it wasn’t so useful.

Ruby V