A new video investigation by the Wall Street Journal finds the key to TikTok's success in how the short-video sharing app monitors viewing times.
Why it matters: TikTok is known for the fiendishly effective way that it selects streams of videos tailored to each user's taste. The algorithm behind this personalization is the company's prize asset — and, like those that power Google and Facebook, it's a secret.
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How they did it: WSJ created a batch of individualized dummy accounts to throw at TikTok and test how it homed in on each fake persona's traits.
What they found: TikTok responds most sensitively to a single signal — how long a user lingers over a video. It starts by showing new users very popular items, and sees which catch their eyes.
The TikTok algorithm works so well that some people think it's reading their minds.
Yes, but: The investigation also found that TikTok — like YouTube — can lure users deep into rabbit holes of increasingly extreme content.
Go deeper: Watch the video.
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