Written By Hello Windows Insiders, today we are releasing Windows 10 Insider Preview Build 21277 (RS_PRERELEASE) to Windows Insiders in the Dev Channel. As mentioned here, we are giving Windows Insiders in the Dev Channel the option to receive builds from the RS_PRERELEASE branch. These builds will be offered as an optional update through the “seeker” experience in Windows Update. This means Insiders will have to go and choose to install the currently offered RS_PRERELEASE build. Once they do, they will continue to receive RS_PRERELEASE builds going forward. This optional experience for receiving RS_PRERELEASE builds is just temporary – we plan to move all Insiders in the Dev Channel back to receiving builds from RS_PRERELEASE sometime after the holidays. As a reminder, Dev Channel builds are not matched to a specific Windows 10 release.