Windows 10 build 21277

Windows 10 build 21277 is the first Insider Preview build of Cobalt, the 21H2 development semester of Windows as a service. It was released to the Windows Insiders in the Dev Channel on 10 December 2020 along with Iron build 20277. The Enterprise LTSC variant was publicly shared on 21 November 2024.
At the time of this build's release, the Dev Channel went under a temporary splitting of released builds. While the channel still received mandatory updates from the Iron semester, builds from this version would be released at the same time as optional updates, giving Insiders the ability to choose to keep receiving Iron builds or move to the new semester.
== New features and changes ==
=== Shell ===
Many features such as the redesigned touch keyboard, emoji picker, voice typing, and theme-aware splash screens that were previously removed in Iron build 20246 have been reintroduced in this build that were made available to a subset of users. In addition, the Meet Now integration on the Windows taskbar introduced in Iron build 20221 has been added to Enterprise SKUs and Azure Active Directory (AAD) user accounts by default.
=== User interface ===
The animations for opening and closing windows have been changed to a simpler effect. Additionally, Aero Shake is also disabled by default.
=== Applications ===
* Snip & Sketch can be used to create a screen snip and paste it directly into a File Explorer folder to save the screenshot there. This change was initially added to the Beta Channel in Feature Experience Pack build 120.2212.1070.0.
* The legacy Snipping Tool application is now an optional feature and can be manually uninstalled via the Settings application.
* Mixed Reality Portal's setup screens now features a video showing a headset and some experiences.
* The scaling logic of the graphs in Task Manager’s Performance tab has been adjusted.
== Bugs and quirks ==
* The update process to this build has a chance of hanging for extended periods of time.
* Some users might see a popup that says “Your PC ran into a problem and will restart in 1 min” after logging in to Windows with either an Azure Active Directory or Active Directory account. If encountered, save any data immediately and let the PC restart.
* File Explorer might hang or crash in this build.
* Live preview doesn't work for pinned site tabs on some machines, a gray window is seen instead of the intended content.
* The modern Disk Management page located at Manage Disks and Volumes is completely blank, and as a result it will not display any drives present on the system. To workaround this issue, use the legacy Disk Management tool (diskmgmt.msc) to manage disk drives.
== Gallery ==
=== Setup ===
Win8boot.png|Boot screen
21277 Setup.png|Setup initial page
21277 EULA.png|EULA
21277 CopyingFiles.png|Copying files
21277 SettingUpDevices.png|Setting up devices
21277 OOBE.png|OOBE
===General===
File:21277 Emojis.png|The emoji picker showing some of the new and gender-neutralized emojis
File:21277EmojiDemo.png|Notepad demo showing some of the new emojis
File:21277 OptionalFeatures.png|Optional Features Settings showing Snipping Tool
File:21277 Animations.gif|New window animations
File:2x277-upgrade.png|Windows Update Settings showing Iron build 20277 downloading and this build offered at the same time
===Enterprise LTSC edition===
File:Windows 10 build 21277 (Enterprise LTSC)-Desktop.png|Desktop
File:Windows 10 build 21277 (Enterprise LTSC) - Winver.png|Winver
File:Windows 10 build 21277 (Enterprise LTSC)-Start1.png|Start menu
File:Windows 10 build 21277 (Enterprise LTSC)-Start2.png|Ditto, in Light mode
File:Windows 10 build 21277 (Enterprise LTSC)-Settings.png|Settings
File:Windows 10 build 21277 (Enterprise LTSC)-About.png|About
==External links== 
*Official announcement
Category:Cobalt builds
Category:Windows 10 builds