• Microsoft shares fell more than 6% on Thursday after guidance fell short of analysts' estimates.
• It's the steepest drop since October 2022.
• For the quarter that ended in September, revenue increased 16%, topping estimates.

Microsoft's better-than-expected earnings report wasn't enough to prevent the stock's steepest sell-off in two years, as investors instead focused on the company's forecast for the current period.

Microsoft shares fell 6% on Thursday and headed for their worst day since Oct. 26, 2022, when they dropped 7.7%. That was a month before the public release of ChatGPT from Microsoft-backed OpenAI, a launch that set the stage for a boom in artificial intelligence investments.

For the period ending in December, Microsoft called for revenue in the range of $68.1 billion to $69.1 billion, implying 10.6% growth at the middle of the range. Analysts surveyed by LSEG were looking for $69.83 billion in revenue.

Revenue in Microsoft's cloud infrastructure business, Azure, increased 33%. CFO Amy Hood said on a call with analysts that growth, in constant currency, will come in at 31% to 32% in the fiscal second quarter.

On Tuesday, Google reported 35% annual growth in its rival cloud business to $11.35 billion. Amazon, which leads the cloud infrastructure market, is scheduled to report results after the close on Thursday.

"We view Q1 results as solid across the core Azure and Office growth businesses, though tempered by a softer Q2 outlook," analysts at BofA Global Research wrote in a report on Thursday. They still recommend buying the stock.

Fiscal first-quarter revenue increased 16% from a year earlier to $65.59 billion, exceeding the average analyst estimate of $64.51 billion, according to LSEG. Earnings per share of $3.30 topped the $3.10 average estimate.

Net income rose 11% to $24.67 billion from $22.29 billion in the year-ago quarter.

Outside suppliers are late in delivering data center infrastructure to Microsoft, meaning the company won't be able to meet demand in the fiscal second quarter.

"I feel pretty good that going into the second half of even this fiscal year, that some of that supply-demand will match up," CEO Satya Nadella said on the earnings call.

Microsoft's AI investments continue to be a major focus for investors, as the company builds out its infrastructure and ramps up chip spending to handle heftier workloads. Microsoft has invested close to $14 billion in OpenAI, which was valued at $157 billion in a financing round earlier this month.

Hood said on the call she expects the company to take a $1.5 billion hit to income in the current period, mainly because of an expected loss from its investment in the AI startup.

Meanwhile, spending on property and equipment grew 50% year over year to $14.92 billion. The consensus among analysts polled by Capital IQ was $14.58 billion.

As of Thursday's close, Microsoft shares were up a little over 8% for the year, while the Nasdaq has risen 21% during the same period.

— CNBC's Ari Levy contributed to this report.

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