Windows 10 build 16257 (rs prerelease)

Windows 10 build 16257 (rs_prerelease) is the second Insider Preview build of Windows 10 April 2018 Update. This build was released to Windows Insiders that were opted into Skip Ahead on 2 August 2017.

Changes

 * Introduced Eye Control, a feature designed for people with disabilities to operate an on-screen mouse, keyboard and a text-to-speech experience by using only their eyes. It requires a compatible eye tracker to use it. The features of Eye Control are detailed in the release announcement.
 * Gave Microsoft Edge an improved look inspired by Fluent Design.
 * Command Prompt had its color values changed to improve the readability of darker colors.
 * Improvements to IME and the touch keyboard.
 * Various improvements to Windows Defender Application Guard.
 * Various other improvements and bug fixes.

Bugs

 * There's a chance that the Start menu, Action Center, and notification toasts will have a background that is 100% transparent. To fix it, either end  via Task Manager or restart the PC.
 * Action Center may show it has a number of notifications, but when it is clicked, there are no notifications to be seen.
 * Sometimes if suggested apps are turned off, sometimes they will appear anyway. If this bug is encountered, navigate to Settings -> Personalization -> Start -> and then toggle “Occasionally show suggestions in Start”.
 * When you install or update a Windows Store app, you may encounter error code 80070057.
 * After upgrading to this build, the Virus and Threat Protection part in Windows Defender Security Center will show as "unknown". Reboot the PC to fix it.