DeepSeek’s AI assistant became the No. 1 downloaded free app on Apple’s iPhone store Monday, propelled by curiosity about the ChatGPT competitor. Part of what’s worrying some U.S. tech industry observers is the idea that the Chinese startup has caught up with the American companies at the forefront of generative AI at a fraction of the cost.

U.S. tech stocks, including Nvidia, Oracle and Google, plummeted Monday after Chinese startup DeepSeek said it created an AI system that can compete against chatbots such as OpenAI's ChatGPT at much lower costs.

DeepSeek, a Hangzhou-based startup founded in 2023, shot to the top of Apple’s App Store free app chart after releasing a new open-source AI model it says rivals OpenAI's work. Its website was hit by outages amid a spike in interest.