Microsoft is kicking off its Build 2017 developer conference in Seattle this morning with a new milestone: The company says Windows 10 is now running on 500 million active monthly devices, up from 400 million last September.

Satya Nadella, the Microsoft CEO, is expected to tout the new number in his opening Build keynote address this morning. The announcement is meant to help make the case for Microsoft’s relevance in an era when the attention of its core developer base is increasingly divided among a variety of competing operating systems and cloud platforms, including Android, Apple iOS, Chrome OS, Amazon Web Services, and Google Cloud.

Microsoft CEO Satya Nadella. (GeekWire File Photo)

The Build conference will focus on underlying developer technologies — including new cloud services, database systems and artificial intelligence tools. And Microsoft itself is increasingly making apps and services that work with rival technologies and platforms.

Announcements this morning will include a preview of Azure IoT Edge; new database technologies including Azure Cosmos DB; the general availability of Visual Studio 2017 for Mac; and the public preview of the Cortana Skills Kit, allowing developers to tap into Microsoft’s virtual assistant, which now has 141 million monthly active users.

Also notable is the growing cloud footprint of Office, with the company now citing more than 100 million commercial Office 365 monthly active users. In Office news, the company will be showing new capabilities for developers making apps for Microsoft Teams, its chat-based collaboration tool that launched this year to rival Slack.

But the global reach of Windows is still one of Microsoft’s biggest selling points for developers.

Windows 10 usage is well short of the 1 billion devices that Microsoft had originally aimed to reach by the middle of next year, but the company long ago abandoned that goal as it scaled back its smartphone ambitions.

In additional to traditional PCs and tablets from Microsoft and its hardware partners, Windows 10 devices also include the Xbox One console and its HoloLens mixed reality devices, available to developers and enterprise customers.

Microsoft last week made a new push into the education technology market with the unveiling of the Windows 10 S operating system, designed for schools, and the announcement of the new Surface Laptop. The company is expected to unveil new details about its next Xbox console in June at the E3 video-game convention.

The new numbers follow the release of the Windows 10 Creators Update last month. Windows 7 is still the most-used version of the Microsoft OS on the desktop, with more than 48 percent of the global market, according to NetMarketShare data. Windows 10 is second with 26 percent of the market.

Special note: All Build conference attendees in Seattle this week receive a special 15% discount to the inaugural GeekWire Cloud Tech Summit, taking place in Bellevue, Wash. on June 7th, and featuring speakers such as Microsoft Azure chief Scott Guthrie; Docker COO Scott Johnston; Cloud Foundry executive director Abby Kearns, Kubernetes co-creator Joe Beda and many others. Use the code — Build15 — when registering on the event site here.

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