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You stop for half a second on a video, even one you do not like, and the app notes it. A program picks your next video out of millions, faster than you can swipe. A person at TikTok or YouTube almost never does. Learn how it works: watch time, why clickbait stopped working, embeddings, how the app finds and ranks videos, what a new account sees, the surprise videos in your feed, and the filter bubble.
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