Windows 10 build 21277

Windows 10 build 21277 is the first Insider Preview of Cobalt. It was released to Insiders on the Dev Channel on 10 December 2020 for those who are opted in via optional updates.

Changes

 * x64 emulation is now available as a preview for Windows 10 on ARM PCs
 * Support for Unicode Emoji 12.1 and 13.0 has been added. This includes over 200 new glyphs, a new gender-neutral design, and some existing emojis being redesigned.
 * The animations when opening and closing a window have been updated to make the transition smoother.
 * You can now use the Snip and Sketch app to create a screen snip and paste it directly into a folder of your choice in File Explorer to save the screenshot there. This change was initially added to the Beta Channel as part of the Feature Experience Pack update.
 * The legacy Snipping Tool is now an optional feature, and it can be uninstalled if preferred from Optional Features Settings.
 * The scaling logic of the graphs in Task Manager’s Performance tab has been adjusted.
 * The Find window, renaming a key, and other places on the Registry Editor all now support CTRL + Backspace to delete words at a time.
 * The folder logic in Start menu’s all apps list has been updated so that if a folder only contains a single item, it'll be now displayed individually.

Bugs

 * Live preview doesn't work for pinned site tabs on some machines.
 * Some users are seeing error 0x80070426 when using their Microsoft account to sign into various apps. Restarting usually fixes this.
 * The modern Disk Management page (Settings → System → Storage → Manage Disks and Volumes) in the Settings app is blank, as a result, it won't display any drives present. To workaround this issue, use the classic Disk Management tool to manage disk drives.