Duolingo shares rose nearly 7 Thursday after a significant surge in users signing up to learn Mandarin. The surge coincides with the growing popularity of Chinese social media app RedNote, a TikTok competitor. The company reported a more than 200 increase in Mandarin learners compared to last year, outpacing the 40 growth for Spanish, a top language on the platform. RedNote is now the top free app on Apple's app store, benefitting from a potential U.S. TikTok ban. U.S. downloads of RedNote surged 20-fold last week. Shares of Duolingo rose over 40 last year, outperforming the Nasdaq’s nearly 30 gain.