Earlier today, Microsoft released a new Dev Channel build for Windows 11 Insiders in the form of build 26120.1252 under KB5038603. Alongside the bug fixes and several other miscellaneous improvements in the build, Microsoft has announced a new feature called "checkpoint cumulative updates."
This is another Windows Update-related improvement Microsoft is making similar to one where IT and system admins can manage feature update installations instead of them being forced.
In a separate blog post on Microsoft"s Tech community website, Maliha Qureshi, a Principal Program Manager Lead at the company, has explained what it is and how it will work. Qureshi writes:
With Windows 11, version 24H2, we’re introducing a new concept of checkpoint cumulative updates. This will allow you to get features and security enhancements via the latest cumulative update through smaller, incremental differentials containing only the changes since the previous checkpoint cumulative update. This means that you can save time, bandwidth, and hard drive space.
Going forward, Microsoft might periodically release cumulative updates as checkpoints. The subsequent updates will then consist of:
- The update package files associated with the checkpoints
- New update package files that contain incremental binary differentials against the version of binaries in the last checkpoint
This process may be repeated multiple times, thereby generating multiple checkpoints during the lifecycle of a given Windows release. The Windows 11, version 24H2 servicing stack can merge all the checkpoints and only download and install content that’s missing on the device.
Hence, essentially, the idea behind the feature is smaller Windows update downloads and that means updates will also apply faster. Consequently, enablement packages for major feature updates can also be installed quickly due to lowered sizes.
Microsoft explains that Windows 11 24H2 will have a new way to deliver such feature updates so that binary differentials in subsequent cumulative updates are generated only for the latest checkpoint instead of the RTM (release to manufacturing) version, which has been the case so far since the original Windows 11 version 21H2 release.
This essentially means that a cumulative update (C.U.) used to be the cumulative of all changes since the RTM, but that will no longer be the case with Windows 11 24H2 and Server 2025. Additionally, thanks to such checkpoint files, Microsoft says that server-side load will also be subsequently reduced.
You can find more details about checkpoint cumulative updates here on the official Microsoft Tech community blog post.