Alphabet’s stock tumbled 12.6% on Thursday, erasing half a trillion dollars in market value – a fallout linked to its own AI‑driven search feature.
Key points
- Alphabet’s AI‑focused “AI Mode” search feature is currently reducing ad inventory, contributing to weaker advertising revenue.
- The company is committing over $200 billion this year to AI infrastructure, double its 2025 spend, and has secured more than $1 trillion in multiyear agreements.
- The share decline triggered broader market weakness, pulling down the Nasdaq, S&P 500, semiconductor stocks, and even industrial firms like Caterpillar.
Shares of Alphabet Inc., the parent of Google, fell 12.6% on Oct. 29, 2026, marking the company’s worst single‑day loss and wiping out roughly $500 billion in market value, according to NBC News. The decline is the second‑largest one‑day wipeout in U.S. market history, trailing only Nvidia’s $589 billion plunge in January 2025.
Investors were told that part of the revenue shortfall stems from Google’s newly rolled‑out “AI Mode” search feature, which delivers fewer ad slots. A senior Alphabet executive explained that the AI‑driven interface is currently suppressing ad inventory, though the company is testing “ad experiments” that have shown “promising results,” senior vice‑president Philipp Schindler said on the earnings call.
Record‑setting share decline
The share slide comes as Alphabet disclosed it has committed to more than $1 trillion in multiyear spending agreements to fund AI infrastructure, energy and data‑center leases. The firm said it expects to spend over $200 billion this year – double the amount budgeted for 2025 – and raised nearly $80 billion in capital in June to support the build‑out.
The sell‑off dragged the Nasdaq Composite down 1.38% and pulled the S&P 500 lower by about 0.3%. Semiconductor makers that supply AI data‑center equipment fell in tandem, with the Philadelphia Semiconductor Index down 1.4%. Even non‑tech stocks felt the shock; Caterpillar, a key supplier of construction equipment for data centers, saw its shares plunge 9.2%, making it the Dow’s second‑worst performer after Alphabet.
AI Mode and ad revenue pressure
While Alphabet’s results lagged, rival Microsoft posted stronger earnings, briefly lifting its shares before they steadied. Analysts see the episode as a warning that the massive capital outlays required for generative‑AI may pressure earnings for years to come, especially if new product features like AI Mode curb traditional ad revenue.
Reader questions
Why did Alphabet’s stock fall so sharply?
Investors reacted to weaker‑than‑expected advertising revenue, which the company linked to its new AI Mode search feature that serves fewer ads, combined with concerns over the scale of its AI‑related spending.
What is the “AI Mode” feature and how does it affect ads?
AI Mode is a search interface that uses generative AI to answer queries. According to a senior executive, the feature currently displays fewer ad slots, which has dampened ad revenue.
How much is Alphabet planning to spend on AI this year?
Alphabet said it will spend more than $200 billion on AI infrastructure and related costs in 2026, double the amount it spent in 2025, and it has over $1 trillion in multiyear spending agreements.
Source: nbcnews.com
