Google parent company stock plunges $500bn amid AI fears, worst day ever

Google's parent company, Alphabet, saw its market value plummet by approximately $500 billion on October 29, 2026, marking one of its most significant single-day stock declines. This dramatic drop was largely fueled by investor anxiety surrounding the company's artificial intelligence (AI) initiatives and their impact on its core search advertising business. Shares hit a multi-month low as revelations about the monetization of AI-powered search features concerned Wall Street.

Concerns stemmed from Google's third-quarter earnings report, which indicated that AI Mode queries were generating less revenue than traditional search methods. This, combined with a slowdown in overall search advertising growth and considerable capital expenditures for AI infrastructure, resulted in negative free cash flow.

The market's reaction highlights broader apprehensions within the investment community regarding the financial returns and disruptive potential of AI technologies on established business models, particularly for tech giants heavily invested in the evolving AI landscape.