The initial Cobalt-based release was made generally available on 5 October 2021 as a free upgrade served through the Windows Update service, and includes a refreshed user interface, as well as other minor improvements over Windows 10. Windows 11 (codenamed Sun Valley, also internally referred to as Windows SV) is a major version of Microsoft Windows that was originally announced on 24 June 2021 and succeeds the Windows 10 family of operating systems.