Windows 10 build 21257
| Build of Cobalt | |
| OS family | Windows 10 (NT 10.0) |
|---|---|
| Version number | 10.0 |
| Build number | 21257 |
Windows 10 build 21257 is a build of Cobalt, the 21H2 development semester of Windows as a service. Several issue related to this build were posted to GitHub by different Microsoft employees on 13 November 2020.[1][2]