Windows 8.1 Build 9428 is a pre-release build of the Microsoft Windows 8.1 operating system. A screenshot purported to be of this build had spread onto the Internet, but was later proven to be fake. The build tag of an internal WinJS build from the Windows Store had the same build number, Microsoft.WinJS.2.0.Preview_1.0.9428.0_neutral__8wekyb3d8bbwe, which is a testament to the build's authenticity.