Duolingo shares rose nearly 7% on Thursday following a large spike in users signing up to learn Mandarin in conjunction with soaring usage of Chinese social media app RedNote, a TikTok rival.

The company confirmed to CNBC that there’s been a 216% increase in Mandarin learners using the app compared to a year earlier. For context, Spanish, one of the most popular languages on the app, has seen a 40% increase over the same period, Duolingo said.

RedNote, or Xiaohongshu, as it’s known in China, has rocketed to become the No. 1 free app on the Apple app store, a position it’s held for most of this week. Rounding out the top five are TikTok’s Lemon8 app, U.S. social media upstart Clapper, OpenAI’s ChatGPT and Meta’s Threads.

Last week, the Supreme Court heard oral arguments in the case involving the future of TikTok in the U.S., and a law that could effectively ban the popular app. The justices appeared to favor upholding the law, and a decision could come as soon as Friday. TikTok is reportedly preparing for a U.S. shutdown on Sunday.

RedNote has so far been the top beneficiary of the American user exodus, seeing its U.S. app downloads increase by 20 times over the last week, according to market intelligence firm Sensor Tower. A Duolingo spokesperson told CNBC that the company’s marketing team is “forward-thinking and already has an active presence on Red, managed by our team in China.”

Duolingo offers online and mobile courses across 42 languages. According to its website, Duolingo has 48.8 million Spanish learners. French is the second most popular language on the app at 27.3 million users, while Chinese is eighth at 10.7 million.

Duolingo shares climbed 43% last year, topping the Nasdaq’s 29% gain.

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