Alphabet Inc. (GOOGL) has a list of explanations for why Google Search is losing momentum, and it includes everything from currency swings and European customs rules to even the World Cup advertising calendar. The bigger puzzle: Search queries grew at their fastest pace in five years, yet revenue growth slowed sharply, raising questions about whether Google can turn rising AI-driven engagement into advertising dollars.

Google Search and other revenue rose 12% year over year to $63.35 billion in the third quarter, down from 17% growth in the second quarter and 19% in the first.

Four Factors Behind the Slowdown

Chief Business Officer Philipp Schindler outlined the factors during Alphabet's third quarter earnings call on Wednesday, responding to a question from JPMorgan analyst Doug Anmuth about the disconnect between query growth and revenue.

Foreign exchange was the single largest driver of the slowdown compared with the second quarter, Schindler said. Alphabet also cited weaker spending by some Asia-Pacific retail advertisers affected by the European Union's elimination of its duty-free exemption for low-value parcels.

Effective July 1, the EU replaced its €150 (~$167.13) customs duty exemption with a €3 (~$3.34) duty per item, making the third quarter the first full quarter under the new rules. Alphabet did not identify the affected advertisers.

The World Cup provided another explanation. Media and entertainment advertising normalized after an unusually strong second quarter, when the tournament's schedule concentrated more matches, and associated advertising budgets, in June rather than July.

AI Adds a Monetization Problem

There is another complication that could prove more persistent than currency swings or advertising calendars: AI-powered Search.

Anmuth noted in an Oct. 29 research report that Google's query growth reached a five-year high even as Search revenue growth decelerated. He believes AI Mode is becoming a larger share of queries but likely generates less monetization than traditional Search because it has lower advertising load and coverage.

Google is expanding ads in AI Mode and AI Overviews to more users and international markets. But until those formats generate revenue more comparable to traditional Search, stronger engagement may not translate into equivalent advertising growth.

Q4 Headwinds Still Ahead

Chief Financial Officer Anat Ashkenazi warned that foreign exchange would remain a headwind in the fourth quarter, particularly for Search and YouTube. She also expects tougher year-over-year comparisons to weigh on Search growth by a couple of percentage points.

Anmuth expects near-term Search growth to remain under pressure, although he views the headwinds as more navigable than permanently structural.

Currency, EU customs changes and the World Cup help explain Alphabet's latest slowdown, but AI monetization is the bigger strategic question. Google is attracting more searches; investors now need to see whether it can turn that engagement into sustainable advertising revenue.