SEATTLE >> Amazon unveiled the financial performance of its powerful growth engine for the first time on Thursday, and the numbers sure looked pretty — especially compared with big companies like Microsoft and Google that are chasing it.

While Amazon is primarily known as an online retailer, its revenue and its stock market returns for years have been energized by an entirely different kind of commerce: renting processing power to startups and, increasingly, established businesses.

Amazon helped popularize the field — known as cloud computing — and largely had it to itself for years, an enormous advantage in an industry where rivals usually watch one another closely.

But the other tech powerhouses have since awakened to the fact that they were nowhere in a market that could soon be worth hundreds of billions of dollars. Microsoft, Amazon’s crosstown rival, is especially committed to the challenge, and is in furious pursuit.

At the moment, there is no contest: Amazon is dominant and might even be extending its lead. Its resources, however, are fewer than most of its competitors, who have tens of billions of dollars stashed away. And if there is one thing that cloud computing demands, it is heavy investment to set up enormous data centers around the globe.

Amazon said in its first quarter earnings report that its cloud division, Amazon Web Services, had revenue of $1.57 billion during the first three months of the year. What is more unusual at a company that often reports losses, the cloud business is generating substantial profits. The company said its operating income from AWS was $265 million.

That was more than many analysts had expected, and it drove Amazon shares up in after-hours trading by more than 6 percent. After a rough 2014 and an exuberant 2015, the stock is hovering near its all-time high.

Microsoft ranks a distant No. 2 in cloud computing. It is hard to precisely compare the two businesses because of how Microsoft reports its cloud results. Microsoft said Thursday that its annual revenue from its commercial cloud business would be $6.3 billion based on its recent performance, while Amazon said the comparable annual figure for AWS was $5.16 billion.

Microsoft, though, also includes revenue from different online applications into that figure. Its revenue from a cloud business called Azure, which is more directly comparable to Amazon’s cloud services, was recently estimated by Deutsche Bank to be as little as one-tenth of that from AWS.

“Microsoft is a credible player,” said Lydia Leong, an analyst at Gartner, the technology research firm. But, she added, “Amazon is the most common platform for startups.”

AWS began about a decade ago as a way to provide computing power to various divisions of Amazon. It worked so well internally that Amazon began offering it to startups that were struggling to scale themselves.

“You bought some box, waited weeks for someone to set it up and then started using it,” said Matt McIlwain, a venture capitalist with Madrona Venture Group in Seattle. “With AWS you took out your credit card, started doing what you needed to do and paid by the hour. That won over the startup community and the developer community.”