SHENZHEN—Gan Liping pumped her bike across a busy street, racing to beat a crossing light before it turned red. She didn’t make it. Immediately, her face popped up on two video screens above the street. “Jaywalkers will be captured using facial-recognition technology,” the screens said.

Facial-recognition technology, once a specter of dystopian science fiction, is becoming a feature of daily life in China, where authorities are using it on streets, in subway stations, at airports and at border crossings in a vast experiment...