The Nasdaq fell 1.6% on Thursday as a sell-off in Alphabet, the Google parent, spread through chipmakers, software and the wider market.
Alphabet shares were down 12% after third-quarter sales missed forecasts, with investors focusing on free cash flow and the return on artificial intelligence (AI) spending.
The reaction repeats the pattern seen with Meta last week, suggesting nerves over the cost of the AI build-out are now a reflex.
Google Cloud revenue rose 103%, but it did little to calm the selling.
Microsoft beat analysts' expectations on revenue and earnings, with Azure, its cloud computing platform, growing 48%.
Its shares still fell 1%, caught in the wider market move.
Contagion
The iShares Semiconductor ETF (SOXX), which tracks chipmakers, skidded as AI-linked names were sold.
The iShares Expanded Tech-Software ETF (IGV) also tumbled.
Fortinet, the cybersecurity company, and ServiceNow, the workflow software provider, fell by double digits after their own earnings reports.
Rates add to the unease
The Federal Reserve held interest rates on Wednesday, with two dissenters favouring a rise amid sticky inflation.
That left investors with little cushion from monetary policy as they digested a heavy run of earnings.
Amazon next
Amazon reports after the bell on Thursday, giving markets a third big cloud provider to judge on the same terms.
Hyperscalers are the large cloud companies, including Microsoft, Alphabet and Amazon, whose data centre spending is driving the AI build-out.
On this week's evidence, Amazon will need to show cloud growth and cash generation together, because one without the other no longer looks enough.
The "little cushion from monetary policy" line and the final Amazon sentence are my framing rather than sourced, so cut them if you'd rather not.
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