The 2013 Microsoft BUILD Developers Conference will kick off today at 12 p.m. EDT/ 9 a.m. PT in San Francisco.

The event will begin with a keynote address, which will be available via live stream on Microsoft's Channel 9 site.

Click here to see the keynote address via live stream.

This year's conference will introduce Windows 8.1, dubbed "Blue", to software and web developers. The developer release version of Windows 8.1 will be available for download today.

The conference will continue until June 28 at the Moscone Center.

Apart from the two-hour keynote address, the annual Hackathon is also taking place, where developers will get hands-on coding experience building apps from scratch using Windows, Windows Phone or Windows Azure.

The Hackhathon started at 6 pm on June 25.

Apart from Windows 8.1, Microsoft may also reveal some more information about the Xbox One gaming system, which will be running on the Windows operating system.

Microsoft's Vice President Steve Guggenheimer gave a preview of what will happen at the 2013 BUILD Conference on the official Microsoft Blog.

"At Build 2013 this week in San Francisco, we will showcase how developers, app builder and companies of all sizes can create experience on the Windows platform to engage consumers, empower employees, solve problem and drive companies.

"We will talk about how developers of all types will be able to use Microsoft's broad portfolio of product level capabilities spanning our devices and services, and show how these capabilities can be used together to address the needs of today's developers."