Google-parent Alphabet's stock price plunges, erasing more than $500 billion in value

Share Add NBC News to Google Oct. 29, 2026, 11:06 AM EDT / Updated Oct. 29, 2026, 1:26 PM EDT By Steve Kopack Shares of Google parent company Alphabet sank Thursday by more than 12%, in its worst one-day performance ever, wiping out more than $500 billion in market value. Alphabet is America’s fourth-largest company, worth a total of $3.42 trillion, as of midday. Still, the amount of value it shed Thursday ranks as the second-worst wipeout in market history, only behind Nvidia’s $589 billion drop in 2025 . The sharp drop in its stock price Thursday was the latest sign of broader anxiety across Wall Street over how long it will take big artificial intelligence companies to see consistent returns on investments worth hundreds of billions of dollars. On Wednesday, Alphabet reported its latest quarterly financial results , revealing that revenues fell short of Wall Street’s expectations. It also reported lackluster advertising sales. The “magnitude” of the slowdown in Google’s search business was “steeper than expected,” JPMorgan Chase analysts wrote in a Thursday morning note. A senior Alphabet executive told investors Wednesday that part of the reason ad revenues from search were underperforming was because of Google’s own “AI Mode” search feature, which was resulting in fewer ads. 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For Subscribers FOR SUBSCRIBERS Cruise company had troubled history before abandoning passengers in Cambodia FOR SUBSCRIBERS Dark money group seeks to undercut Republican candidates with pro-gun voters FOR SUBSCRIBERS Amy Acton’s mom, who called her a ‘liar’ in Ramaswamy ad, faced years of turmoil, records show FOR SUBSCRIBERS FDA plans to update nutrition rules for infant formula FOR SUBSCRIBERS How French student protests over schools escalated into nationwide riots FOR SUBSCRIBERS Trump says Alaska’s Democratic Senate candidate should be prosecuted over Dan Sullivan ballot dispute FOR SUBSCRIBERS Election betting odds became less accurate as primaries neared, report finds FOR SUBSCRIBERS How Colorado became a battlefield in the legal fight between LGBTQ and religious rights FOR SUBSCRIBERS How California prison reforms helped free a serial rapist called ‘America’s creepiest heir’ FOR SUBSCRIBERS Trump’s final campaign swing is taking on a darker tone FOR SUBSCRIBERS Mel Robbins has midterms advice for you FOR SUBSCRIBERS Florida cop charged with possessing dead man’s house had history of misconduct FOR SUBSCRIBERS DHS hack exposes 40,000 employee names and undercover ICE agents, activists say FOR SUBSCRIBERS Rising diesel prices hit school districts hard ahead of the midterm elections FOR SUBSCRIBERS ‘There goes Texas’: The swing county that could determine the state’s next senator Slide 1 of 1 The company said during its July earnings report that it planned to spend more than $200 billion this year, which is double what it spent in 2025. The company in June also raised almost $80 billion in capital, also to spend on the ever-expanding AI build-out. Alphabet’s disappointing results also came against the backdrop of better results from its peer Microsoft , whose shares initially rose in after-hours trading Wednesday and overnight before reversing course to fall about 1.5% by 1:20 p.m. ET Thursday. The big drop in Alphabet shares dragged down the Nasdaq Composite index, which was down 1.5% by the afternoon. The S&P 500 fell slightly less, by about 0.4%. Shares of chip companies that supply equipment for AI data centers followed Alphabet shares lower, with the Philadelphia semiconductor index dropping 1.6%. The bleeding even spread beyond the tech sector, as shares of construction equipment giant Caterpillar — a key supplier of the machines required to build data centers — plunged 9% early Thursday. Caterpillar’s recent earnings report revealed that the company’s revenues beat Wall Street expectations but by less than many traders had hoped. The industrial giant was the second worst performing stock on Thursday in the Dow Jones Industrial Average, behind only Alphabet. The Dow declined slightly more than 200 points. As investors clamor for ever-higher returns from companies linked to the costly AI build-out, stock in firms that only narrowly top earnings targets, like Caterpillar, has been punished with dramatic sell-offs. Follow relevant topics Markets Artificial intelligence See your feed › Share Add NBC News to Google Steve Kopack Steve Kopack is a senior reporter at NBC News covering business and the economy.