Windows 10 build 9780
Windows 10 build 9780 is the earliest available build of Windows 10, which was uploaded to BetaArchive on 26 January 2019. This build was originally released to Microsoft partners participating in the Ecosystem Engineering Access Program (EEAP), as indicated by the fbl_partner_eeap
branch.
Due to its earliness, this build identifies itself as Windows 8.1 in many areas and still bears the 6.3 kernel version.