Does a Windows 10 PC download an entire cumulative update or just the parts it needs

Question

I understand that CU's contain all previous patches for the OS in question but I THOUGHT the Windows Update client / Servicing Stack was smart enough to pick and choose the PARTS of a CU that it needs and save a tonne of bandwidth and time.

For instance, if a PC was patched 3 months ago and now has patches KB001 KB002 KB003 KB004 and KB005 and now (3 months later) Microsoft has released KB006, will that Windows 10 PC:

1: just download/install KB006 but SHOW/REPORT that it is installing the entire CU, or
2: download the entire CU but install only KB006

Thoughts?

Answer 1

I beleive that is mroe due to the way they package it, into cumaltive bundles. If you look at
https://learn.microsoft.com/en-us/windows/deployment/update/how-windows-update-works

It will downlaod everything, becuase it does not look at what it has to install before downloading.

Answer 2

Hello

Thank you for your question and reaching out. I can understand you are having query related to how CU works.

Windows updates are cumulative and contain all previously released fixes to guard against fragmentation of the OS that can lead to reliability and vulnerability issues when only a subset of fixes are installed, and are the only regular monthly releases.

Reference :
https://learn.microsoft.com/en-us/windows/deployment/update/servicing-stack-updates

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