The webcast can be viewed from the Build news website and Microsoft's Channel 9.
Microsoft, as usual, has not listed the keynote speakers, but undoubtedly CEO Satya Nadella will participate -- probably as the opening act before handing off demos and other bits to executives like Terry Myerson, who leads the operating systems group; Joe Belfiore, chief of Windows' design; and Julie White, lead on Office product management. Those three have been prominent speakers at recent Microsoft press events.
Build 2015 runs through Friday at San Francisco's Moscone Center, the locale for the third straight year.
Microsoft is expected to spend much of its time tomorrow talking up Windows 10 and the next generation of Office, both the semi-cloud Office 365 and the on-premises Office 2016, as well as development tools for apps on all three platforms. The Redmond, Wash. company will also probably tout -- again -- the benefits of creating desktop applications and mobile apps for Windows 10.
Microsoft has so far painted its Windows 10 monetization plan in only the broadest terms: Tomorrow would be a good time to have that conversation, as the company must persuade developers that it's in their financial interest to jump on the bandwagon.
It's possible that Microsoft will use the conference keynote to flesh out Windows 10, including a more specific release date. Other information, however, ranging from support timeline to details on the two update tempos offered enterprises, will probably be left for another day.
Executives typically focus on the topic at hand, in this case, development, rather than stray into those other subjects.
Build in general, and the keynote in particular, will be one of the most important pre-launch opportunities for Microsoft to make the Windows 10 case to the media and non-developer enthusiasts, not only for personal computers -- which have been in a sales slump since 2012's June quarter -- but also for mobile.
Gartner last month laid out Microsoft's problem when it estimated that Windows' device operating system share will slip slightly this year to 13.3%, and climb only a percentage point or so -- to 14.4% -- by the end of 2017.
Microsoft has scheduled the Build keynote to run two and a half hours.