On April 2, 2014, Microsoft officially announced the existence of Cortana, its digital assistant, at its Build developer conference. Cortana has since become one on Microsoft biggest properties, expanding to several platforms and adding new features, with more on the way.

Cortana team member Shane Landry noted the two-year anniversary on his Twitter account:

Rumors about Cortana started several months earlier. thanks to a leak of a developer device that showed references to "zCortana" in the code. Cortana, which was named after the A.I. assistant to Master Chief in Microsoft's Halo game series, was officially released to the outside world on April 14, with the launch of the Developer Preview for Windows Phone 8.1.

Cortana has since expanded to Windows 10 and Windows 10 Mobile as an integrated part of the OS. Microsoft has also launched Cortana apps for iOS and Android, although their functionality are not as extensive as found on Windows. At Build 2016 this week, Microsoft announced some upcoming improvements to Cortana, including proactive notifications and lock screen support for Windows 10. It will also be added to the Xbox One later this summer.