Alphabet loses ~$500B in market value as AI spending soars and Search slips below half of revenue

Alphabet shares fell about 13% (12.6% at the close) on Thursday 29 October 2026, the day after its Q3 results, wiping out roughly $500B in market value. It was the stock's worst day since Google listed in 2004, beating the previous record of 11.63% from March 2020. NBC News ranks it the second-largest one-day value loss in US market history, behind Nvidia's $589B drop in January 2025. According to the BBC, Alphabet's market value fell from $3.97T to $3.46T.

Why investors sold

Search revenue grew 12% to $63.35B but missed analyst estimates for the second quarter in a row. Growth slowed from 19% in Q1 and 17% in Q2. Google said its own AI Mode in Search shows fewer ads for now. AI spending also pushed free cash flow negative again, to about -$9.1B against the roughly -$2.7B analysts expected (Q2: -$5.9B). Alphabet kept its 2026 capex guidance of $195B to $205B and said spending will rise further in 2027.

Search falls below half of revenue

Google Search & other generated $63.35B of Alphabet's $127.58B total revenue in Q3 2026, about 49.7%. It is the first time the core search business has made up less than half of the group's quarterly revenue, down from 55.3% a year earlier ($56.57B of $102.35B in Q3 2025). Google Cloud revenue roughly doubled (+103%) to $30.71B from $15.16B, and Cloud operating income rose to $11.12B from $3.59B.

Sources

CNBC: Alphabet tanks nearly 13% for worst day ever
NBC News
BBC
AP
Alphabet Q3 2026 results release (SEC filing)