Alphabet plunges nearly 13% in a day as investors reassess AI spending returns

On October 30, 2026, a brief item surfaced on Hacker News stating that Google's market value had dropped by roughly $500 billion amid AI-related concerns, sending a jolt through Wall Street. The report did not elaborate on the cause, but it underscored investor anxiety over how AI might affect the company's business. The post quickly gained traction, reaching 54 points on Hacker News.

Later the same day, a report from Eastmoney provided more detail. Google's parent company, Alphabet, saw its shares plunge nearly 13% on Thursday, marking the largest one-day drop since Google went public in 2004. The sell-off wiped out approximately $500 billion in market value, or about CNY 3.33 trillion, making it the second-largest single-day market-cap loss in U.S. stock-market history, behind only Nvidia's record in January 2025. The severity of the decline triggered what is known as a "death cross," with the stock's 50-day moving average falling below its 200-day moving average. Some analysts suggested that such a severe loss of momentum could signal further downside.

In its earnings report released after U.S. markets closed on Wednesday, Alphabet disclosed that third-quarter free cash flow came in at negative $9.07 billion, versus analysts' expectations of $2.7 billion. The company maintained its full-year capital expenditure guidance at $195 billion to $205 billion, highlighting the enormous costs it is bearing in the race for data center capacity and the development of new AI models. Alphabet's Thursday plunge dragged down major U.S. indexes, with the Nasdaq Composite falling 1.38%, as it intensified concerns that global AI infrastructure spending may outpace returns. Meanwhile, Microsoft, a direct competitor in several of Google's core markets, ended the day essentially flat, and investors are now focused on how the two tech giants are positioned following their respective earnings reports.