MOUNTAIN VIEW, California: Alphabet Inc., Google's corporate parent, crossed a US$4 trillion market valuation on January 12, underscoring how investor enthusiasm around artificial intelligence continues to reshape the hierarchy of Big Tech.

The milestone came just months after Alphabet emerged largely unscathed from a major U.S. antitrust case. Last year, a federal court ruled that Google's search engine was an illegal monopoly, but stopped short of ordering a breakup of the company. The remedies imposed by the judge were widely viewed by investors as limited, helping to fuel a sharp rally in Alphabet shares. Since that ruling, the stock has climbed 57 percent, adding roughly $1.4 trillion in market value.

Alphabet's surge places it in an elite group of companies with $4 trillion valuations. Chipmaker Nvidia was the first to cross the threshold in July, followed by Apple and Microsoft last year, though both later retreated amid concerns that massive AI spending could inflate a bubble. Nvidia briefly topped $5 trillion in late October before pulling back as similar fears weighed on its stock.

Other tech giants are also benefiting from AI-driven optimism. Amazon is valued at about $2.6 trillion, while Meta Platforms stands at $1.6 trillion. Tesla, now valued at roughly $1.5 trillion, has also tied its future closely to AI, approving a compensation plan that could eventually pay CEO Elon Musk $1 trillion if aggressive performance targets are met, including an $8.5 trillion market valuation.

Alphabet reached the $4 trillion mark on the same day Apple announced it would rely on Google's AI technology to enhance its Siri virtual assistant, after struggling to deliver more advanced features internally. That partnership highlights Google's growing influence in the AI ecosystem.

The company has been weaving AI deeper into its core businesses, transforming its search engine into a more conversational tool to compete with rivals such as OpenAI's ChatGPT and Perplexity. Its latest Gemini model has received strong reviews, helping push Alphabet's stock higher even as shares of some other AI-focused firms have wobbled. Google Cloud, which sells AI tools to businesses and governments, has become Alphabet's fastest-growing division over the past three years. AI advances have also enabled its Waymo unit to expand robotaxi services across multiple U.S. cities.

The pace of innovation was one factor cited by U.S. District Judge Amit Mehta in rejecting the Justice Department's request that Google be forced to sell its Chrome browser. The judge said rapid technological change driven by AI was already reshaping online search.

Still, risks remain. Alphabet's valuation could fall sharply if investor sentiment turns against AI-heavy stocks. CEO Sundar Pichai has acknowledged that markets may be getting ahead of themselves.

"I think no company is going to be immune, including us," Pichai said, if AI-driven enthusiasm fades.