Microsoft is still testing its upcoming Windows Phone 8.1 update internally, but a leaked screenshot reveals how the company is moving to on-screen buttons in the future. The tiny image, published by @evleaks, shows the standard back, Windows, and search buttons all on-screen in a Windows Phone 8.1 screenshot. We have mocked up how the on-screen buttons are displayed alongside the Windows Phone 8.1 Start Screen in an image below. We understand that Microsoft is removing the physical button requirement in an effort to lower costs for device manufacturers.