DeepSeek, a Chinese AI startup, saw its iOS app surge to the top of Apple's App Store just days after launching its latest reasoning model, DeepSeek R1, leaving OpenAI's ChatGPT in second place. DeepSeek claims that DeepSeek R1 beats competing AI models in several key benchmarks. The app's popularity is propelled by the fact that it is open source, free to use on the web and as a smartphone app, and charges a lot less for API access than OpenAI. DeepSeek is now the top app on Apple's App Store and the 20th most popular app on Google Play. The launch and sudden popularity of DeepSeek could impact the U.S. stock market, where Nvidia currently reigns supreme as the largest company by market cap, as there are indications that DeepSeek has been built and trained for far less than competing U.S.-based models, potentially meaning weaker demand for Nvidia hardware. Currently, tech stock index NASDAQ's futures are down 3.2 percent ahead of market open on Monday.