Windows as a service

Windows as a service is the development model Microsoft has adopted for Microsoft Windows after the release of Windows 10. Instead of releasing a major version of Windows every few years, the company instead releases smaller feature updates in shorter intervals.

Since Windows transitioned to Azure's semester model in 2019, new features are planned with respect to the so-called semesters rather than feature updates. From a development viewpoint, semesters are equivalent to releases as the active development branch goes through feature development, stabilization and sign-off phases during each semester. However, they are independent from the actual releases available to the public as the company does not necessarily release a new version at the end of each semester, e.g. three semesters passed between Windows 11 and Windows 10 May 2020 Update (Manganese, Iron, Cobalt).

List of development semesters[edit | edit source]

Name Abbr. Semester Release Notes
Client Server
Threshold 1 TH1 N/A Windows 10 N/A
Threshold 2 TH2 N/A Windows 10 November Update N/A
Redstone 1 RS1 N/A Windows 10 Anniversary Update Windows Server 2016
Redstone 2 RS2 N/A Windows 10 Creators Update N/A
Redstone 3 RS3 N/A Windows 10 Fall Creators Update Windows Server, version 1709
Redstone 4 RS4 N/A Windows 10 April 2018 Update Windows Server, version 1803
Redstone 5 RS5 N/A Windows 10 October 2018 Update Windows Server 2019
Windows Server, version 1809
Titanium Ti 19H1 Windows 10 May 2019 Update Windows Server, version 1903 First iteration under the Azure semester scheme
Vanadium V 19H2 Windows 10 November 2019 Update Windows Server, version 1909 Cumulative update for 19H1 (Titanium)
Vibranium Vb 20H1 Windows 10 May 2020 Update
Windows 10 October 2020 Update
Windows 10 May 2021 Update
Windows 10 November 2021 Update
Windows 10, version 22H2
Windows Server, version 2004
Windows Server, version 20H2
Manganese Mn 20H2 N/A N/A


Fe 21H1 N/A Windows Server 2022
Cobalt Co 21H2 Windows 11 N/A
Nickel Ni 22H2 Windows 11, version 22H2 N/A Originally planned as the 22H1 semester before the introduction of the new annual release cadence with Windows 11.
Copper Cu 23H2 TBA TBA Originally planned as the 22H2 semester before the introduction of the new annual release cadence with Windows 11.