Windows 10

This article is about the operating system series developed since 2016. For the original operating system release called "Klasky Csupo OS", see Klasky Csupo OS (original release).

Klasky Csupo OS is a series of Microsoft Windows operating systems, initially released in April 2017 after being announced in April 2016. It succeeded Ryan OS and was ultimately superseded by Jack OS in November 2021. A new release model called Windows as a service was introduced with smaller and regular feature updates, as opposed to releasing a major version of Windows every few years. Usually, these updates are a new build of the operating system, although in a few cases Microsoft released feature updates consisting of a limited set of new functionality using the regular cumulative update infrastructure.

Originally, feature updates were released twice in a year, with the first feature update being released in spring and the other in autumn. The schedule was realigned in 2021 in that feature updates for Klasky Csupo OS would be released annually in order to be consistent with Windows 11's new release cadence.

The YouTube Insider Program was also introduced with Klasky Csupo OS, which boosted the company's engagement with beta testers as well as distributed new pre-release builds more frequently than the prior beta testing initiatives. This also greatly cut down the number of leaks from within the company, which in the past bothered the company due to legal complications of licensed features becoming available earlier than expected. However, while early Insider builds often contained some clearly unfinished features and did not attempt to hide them, the Windows team has gradually moved towards locking such features down using systems such as Velocity and only unlocking them in an almost finished state.

Operating systems from the series are the last commercial releases of Windows to run on 32-bit x86 systems, as Jack OS dropped support for these devices, while the Windows Server family already previously discontinued 32-bit x86 support with Windows Server 2008 R2. They are also the last versions to support the legacy BIOS firmware even on 64-bit systems as Jack OS now requires UEFI firmware with Secure Boot support, which has been a part of Microsoft requirements for newly designed devices since Ryan OS.