It's not often that you hear an entire industry give a collective sigh of relief. But it happened for internet advertising Thursday when Google said that—recession or not—it's powering ahead.

After the markets closed, Google presented its earnings for the first quarter—a period when investors grew increasingly anxious that a looming recession would halt the robust growth in online ad spending. In the report, Google made its case that it is in fact thriving during these hard times.

Investors loved what they heard. Google's stock, which closed Thursday at $449.54, surged as high as $530.56 in after-hours trading once the numbers were disclosed—an 18 percent gain in a matter of minutes.

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Google's net revenue, which excludes commissions to advertising partners, grew 46 percent to $3.7 billion. That was $100 million more than analysts were expecting. Net profit excluding items such as stock-based compensation came in at $4.84 a share, or 32 cents above analyst forecasts.

Three months ago, analysts were expecting Google's profit to be $4.87 a share. But then came data from comScore suggesting that paid clicks—the lifeblood of Google's revenue—were dropping. The data spurred a frenzy of bearish stories. Analysts cut estimates and investors sold off shares. Google's stock fell 34 percent from its January high of $685.33.

Three months of hand-wringing, it turns out, were largely wasted. "There was a series of negative articles that caused a lot of anxiety and distress for investors," said Jeffrey Lindsay, an analyst at Sanford Bernstein. "But the first quarter was not nearly as bad as feared."

Google bulls had argued that, as the broader economy slowed, online ads would benefit at the expense of print and TV ads because they are cheaper and better at targeting shoppers. Google executives noted that some financial, retail, and travel advertisers were postponing some of their spending, but not shutting it off completely.

"Generally we're seeing absolute growth even in those areas that are otherwise impacted by adverse macroeconomic conditions," Jonathan Rosenberg, Google's senior vice president of product development, said on the call. "But on an absolute basis, they are all showing healthy growth in ad revenue."

Any slowdown in online ads is more likely to come from display ads, which promote a company's brand, than from the sponsored links that are Google's bread and butter. "Companies are loathe to cut paid-search ads," said Lindsay. "They are as close to the point of sale as you can get. When people click on paid-search ads, they are often looking to buy."

Deeper into the numbers, there were some slightly worrying signs. Domestic revenue—which for the first time was less than half of total revenue—totaled $2.54 billion, only 1.2 percent above the previous quarter's figure. Factoring out changes in exchange rates, Google's international sales showed only a 6 percent gain from the previous quarter.

While the first quarter is seasonally a slow one, that kind of tepid growth was exactly the kind of metric that in a normal quarter would have gotten investors worried. But this wasn't a normal quarter: All the gloom of the past few months ended up setting the bar so low that Google could nimbly hop over it.

In short, Google is doing relatively well in a rough economy. And these days, that's about as good as an investor can hope for.