Mining TikTok for the sole purpose of seeing inside a police state is an unorthodox use of the app. TikTok, which did not respond to requests for comment for this article, shot to the top of Apple’s most downloaded list last year, and stayed there—hitting an estimated one billion installs in February. Most people know it as an app popular with teenagers in the US, Europe, and China for its user-generated, snappy, gimmicky short videos cut to pop music. But soon, the app was co-opted by people who understood its potential.

Earlier this year, I reported on the story of Kalbinur Tursun, a woman who managed to flee Xinjiang but was forced to leave her children behind. While casually browsing social media from her home in Istanbul, Tursun saw a TikTok video of her 6-year-old daughter, Aisha, filmed in what appears to be a Chinese orphanage for Uyghur children. It was the first time in years she had seen her daughter’s face.

Though Tursun’s story seems an astonishing coincidence, she’s not the only Uyghur to have discovered news of her missing family by chance through TikTok. In February, Business Insider reported on the story of Abdurahman Tohti, who lives in Turkey and had not heard from his family since they left for Xinjiang on vacation in 2016. “While scrolling through Douyin ... he saw a familiar sight: big, black eyes, and round, rosy cheeks,” reporter Alexandra Ma wrote. “It was his 4-year-old son, Abduleziz.” In the video, an off-camera voice asks: “What’s the name of the Fatherland?” “The People’s Republic of China!” the little boy yells.

Tohti’s story was a turning point for Alip Erkin, the Uyghur activist in Australia. “I realized Douyin was one of the few platforms that people overseas can get some valuable information from,” he said.

The Uyghurs who do this work need to use special tactics to access Chinese TikTok, which is behind China’s firewall, and must be accessed with a Chinese phone.

China’s firewall—originally designed to keep Chinese people from accessing foreign websites—now appears to be also stopping foreigners from seeing in. “It looks like they’re creating a reverse great firewall, and Douyin is a perfect example. They want to keep TikTok outside and Douyin inside; there’s an intentionality there that has an element of censorship about it,” says James Leibold, associate professor in politics and Asian studies at Australia's La Trobe University. Day by day, he says, it’s becoming more difficult to access online content from Xinjiang. The solution, he believes, is to be ever more innovative and methodical.

Once they’ve got around the firewall and accessed TikTok, the international Uyghur activists then have to “teach” the app’s algorithm to show them the videos they want to see. “You have to train it in a certain way,” Yasin said. “You can’t really search, because they cleaned up all the location-based search results. Anything that uses Xinjiang keywords is censored.” TikTok uses algorithms to “serve” users the content it thinks they will like, based on their reactions and responses to each video.

“To make my feed more relevant, I don’t ‘like’ or comment on content other than that about Uyghurs or East Turkestan [the preferred Uyghur name for Xinjiang],” Erkin says. “I only like what I want to see.” That way, he’ll see more videos like it.

It’s a strangely satisfying process, Yasin says. “That’s the beauty of it. Sometimes the algorithm will recommend me something recently posted, not super popular—and it’s what I’m looking for.”

Two months ago, a Uyghur exile escaped Xinjiang and arrived in the United States. She brought her Chinese phone with her—a precious commodity. Using her old phone and Chinese sim card, she now works alongside a group of Uyghur students to mine TikTok. Mehmet Jan, a student in the US, helps run the project. “I categorize the videos into four groups,” he says, sorting them according to whether they show testimonials, surveillance, destruction of mosques, or cultural annihilation.

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The group of students are intent on collecting proof of Xinjiang’s gradual reprogramming into a state built in Beijing’s image.“This is no targeted response to violent extremism, but a concerted campaign to hollow out a whole culture,” scholar Rachel Harris wrote in an article for The Guardian in April.