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.

WATCH: AI will continue to be catalyst for Duolingo

Snap shares closed down 5% on Thursday after the Federal Trade Commission said it would refer a complaint against the company to the Department of Justice.

The FTC’s non-public complaint involves allegations that Snapchat’s My AI chatbot poses “risks and harms to young users,” the commission said in a statement. The complaint stems from the FTC’s compliance reviews with Snap following a 2014 settlement regarding allegations of public deception pertaining to data collection by the company.

As part of the FTC’s compliance reviews of Snap, the agency said it had uncovered the possibility that the company “is violating or is about to violate the law.”

“A proceeding is in the public interest,” the FTC said in its statement.

The FTC did not specify what about the My AI chatbot its complaint was focused on, but the chatbot has previously drawn scrutiny.

A Snap spokesperson pushed back against the FTC’s claims in a statement to CNBC.

“Unfortunately, on the last day of this Administration, a divided FTC decided to vote out a proposed complaint that does not consider any of these efforts, is based on inaccuracies, and lacks concrete evidence,” the Snap spokesperson said. “It also fails to identify any tangible harm and is subject to serious First Amendment concerns.”

The spokesperson added that while the company shares the FTC’s “focus on ensuring the thoughtful development of generative AI,” Snap believes that the “complaint would stifle innovation and competition in a critical and growing sector of the economy.”

Snap debuted the My AI chatbot in 2023. It is powered by the large language models of OpenAI and Google, giving it the ability to answer user questions and provide tips and suggestions similar to ChatGPT and other AI-powered chatting tools.

The chatbot has been noted for providing problematic responses. In one instance while speaking with a reporter who was pretending to be a teenager, the chatbot answered explained how to hide the smell of alcohol and marijuana, The Washington Post reported in 2023. At the time of the chatbot’s initial release, Snap said that My AI, like other AI-powered chatbots, is “prone to hallucination and can be tricked into saying just about anything. Please be aware of its many deficiencies and sorry in advance!”

In Oct. 2023, the United Kingdom’s Information Commissioner’s Office issued a preliminary enforcement notice against Snap, alleging that the company’s My AI-related risk assessment “did not adequately assess the data protection risks posed by the generative AI technology, particularly to children.”

Although the FTC said that it voted during a closed meeting to issue a public statement about it’s case against Snap and its ensuing referral to the DOJ, it noted that FTC commissioners Melissa Holyoak and Andrew Ferguson were absent.

The FTC also pointed to a dissenting statement by Ferguson, who President-elect Donald Trump named in December to replace Lina Khan as the next FTC chair.

Ferguson noted that these kinds of referrals “are not disclosed unless and until the complaint is filed in court by the Department or the Commission.”

“I did not participate in the farcical closed meeting at which this matter was approved,” he wrote.

Ferguson added that he opposes the FTC’s complaint against Snap, but that he can’t “release a detailed analysis of its many problems,” because the case is not public. Ferguson wrote that the complaint’s interpretations of an FTC law is “wrong” and that it is “in direct conflict with the guarantees of the First Amendment.”

If the DOJ files the complaint, Ferguson said he will “release a more detailed statement about this affront to the Constitution and the rule of law.”

Watch: Snap CEO on earnings beat and new advertising products

Apple stock closed down 4% on Thursday, its worst day since Aug. 5, following several reports of lackluster iPhone sales in China.

The iPhone maker’s stock price is down nearly 12% from its most recent peak in December, and it’s the worst-performing of the seven largest technology stocks so far in 2025.

The slide comes after a report Thursday from Canalys, a market research firm, which suggested that Apple had fallen to third place in terms of smartphones sold in China in 2024, behind homegrown manufacturers Vivo and Huawei.

Apple shipped 15% of the 284 million phones sold in China last year, according to the report, but that was down 17% on an annual basis. Vivo and Huawei, meanwhile, saw strong growth.

TSMC, a key Apple supplier, on Thursday reported a smartphone sales forecast for the first quarter that suggested a nearly 6% sequential drop. TSMC, which makes the chips at the heart of Apple’s devices, attributed the drop to seasonality. TSMC said AI chips comprised over half of its revenue in the fourth quarter, displacing smartphones, which had been its largest business.

Notable Apple supply chain analyst Ming-Chi Kuo on Monday wrote that he expects iPhone shipments to decline 6% on an annual basis in the first half of 2025, with most of the decline happening in the second quarter. Kuo wrote that he believes Apple Intelligence, the company’s artificial intelligence system that is not yet available in China, isn’t boosting iPhone demand.

“There is no evidence of Apple Intelligence’s ability to benefit hardware replacement cycles or service business,” Kuo wrote.

Apple reports its December quarter results on Jan. 30.

WATCH: Apple correction due to fundamentals, iPhone 17 upgrades expected, says Morgan Stanley’s Woodring