U.S. tech stocks tumbled after Chinese startup DeepSeek unveiled a low-cost AI chatbot, sparking concerns about the sky-high valuations of tech giants like Nvidia and Microsoft. Patrick Moorhead, chief analyst at Moor Insights,

In a matter of days, DeepSeek proved to be so popular as to climb to the top of Apple's App Store, surpassing OpenAI's ChatGPT as the most downloaded app. But for owners of Nvidia stock, and stock traders in general, DeepSeek is on track of becoming a black swan — an unexpected event with extreme consequences.