Alphabet, Google's parent company, has surpassed Apple to become the world's second most valuable company, driven by a surge in its stock price and AI advancements. The market capitalizations are $3.89 trillion for Alphabet and $3.85 trillion for Apple, marking the first time since 2019 that Alphabet leads Apple in valuation. Alphabet's strong performance is attributed to its Gemini AI model and Tensor Processing Unit chips, making it the best performing stock among major US tech companies in 2025.