"The Cortana search box [in the Windows 10 task bar] has over 100 million monthly active users, with 8 billion questions asked to date," Nadella stated plainly on the call.
Now, the Redmond campus chief didn't specify exactly how many of those users are using Cortana on the desktop with their voice or simply typing into the search box, but how much does that matter?
Regardless of their method – granted, 100 million vocal users would go a long way to improve the virtual assistant's voice recognition – a lot of users are tapping into Cortana's cloud-powered knowledge graph and machine learning, which will all improve the more it's used.
The figure is big enough to draw specific attention to it in an earnings call, at least.
Now, to put that into a bit more perspective, Microsoft has issued 350 million Windows 10 installs as of this May. So, theoretically nearly a third of all Windows 10 users are using Cortana.
And that's not even considering Cortana on iOS and Android
The most specific Apple seems to have ever gotten about Siri's usage statistics was at its WWDC 2016 keynote, wherein SVP of Software Engineering Craig Federighi said that Siri serves over 2 billion requests a week.
That's no doubt an impressive figure, but not as specific and widely recognized a metric as "this many million monthly active users." Monthly active users, or MAU, is the generally accepted metric for an app or service's success.
Alphabet seems to have said even less about how many people are using Google Now, it's Android-based virtual assistant. The firm gave no specific figures during its 2016 Google I/O keynote regarding Google Now usage, though we do know that Google voice searches have doubled over the past year – as of this February.
(An independent Parks Associates study pegs more than half of iOS users regularly using Siri and less than a third of Android users accessing Google Now, figures we should be hesitant to count as they're not from an official source.)
Keep in mind that, while Siri's billions of served requests per week is poised to only grow once macOS Sierra is widely released later this year (and Google Now is accessible virtually from anything that has access to Google.com), Nadella's comment on Cortana usage doesn't include numbers from Android, iOS and Xbox One.
So, it's likely that Cortana's usage on the whole is even bigger than Microsoft is letting on, but probably not by an enormous margin. (That could change as more gamers download the latest version of the Xbox One software.)
Generally speaking, companies don't release MAU figures unless they're large enough to be worth mentioning. On a related note, it's for similar reasons that Microsoft recently opted to stop releasing Xbox One sales figures.
So, is Cortana enjoying more success than its rivals already? That's tough to say without either of its biggest rivals being more specific regarding their offerings. But, what can be said is that Microsoft is enjoying wild success with the assistant within its own ecosystem.
AI and machine learning: a pillar of Microsoft's strategy?
What else can be said that's even more important is that, with numbers like these, you better believe that Microsoft is poised to double down on not only Cortana, but the core concepts behind the virtual assistant: artificial intelligence (AI) and machine learning.
From expanding Cortana's functionality and breadth to investing in bots, these two corners of the computing space have become central to the company's ethos.
Cortana is getting even more tricked out in the forthcoming Windows 10 Anniversary Update, and we should expect the assistant to be even more central to the operating system (OS) come next spring or summer, when the second phase of "Redstone" is expected to land alongside new Surface hardware.
I wouldn't be surprised to see Cortana soon take the wheel in Windows 10 as soon as next year, similar to that of the OS in the film Her, albeit on a far more rudimentary scale.
Sure, everyone's been making projections like this for a while of every major tech firm, but now we have far more concrete evidence of the imminent push. And, with Microsoft seemingly leading the pack in AI and machine learning (despite its stumbles), you can bet that Apple and Alphabet will respond in kind.
Regardless of who is in the lead, what's key to take away from Nadella's awfully specific remarks on Cortana is that A.) it's not going anywhere, and if anything it's only going to grow more central to Windows and B.) the rest of the industry will respond in kind more emphatically than it has already.
Whether you like it or not, AI and machine learning are all but the future of computing. Microsoft may have sorely missed out on the mobile revolution, but it's not about to miss out on the next one.
- Now, what about Microsoft's part in that other revolution, HoloLens?
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Joe Osborne is the Senior Technology Editor at Insider Inc. His role is to leads the technology coverage team for the Business Insider Shopping team, facilitating expert reviews, comprehensive buying guides, snap deals news and more. Previously, Joe was TechRadar's US computing editor, leading reviews of everything from gaming PCs to internal components and accessories. In his spare time, Joe is a renowned Dungeons and Dragons dungeon master – and arguably the nicest man in tech.