

So while ucrtbase.dll is distributed via Windows Update, that doesn't include any of the Visual C++ specific libraries. The Visual C++ redistributable contains - where xxx is the version:

However, the Visual C++ redistributable isn't just made up of the UCRT, and in some cases doesn't even contain the UCRT. To Windows 8 so it went out of support in 2016. Windows 8.1 was seen as a service pack of sorts Windows Vista went out of support in April 2017, so it never had an update which included the UCRT. So as long as you are running a version of Windows that was updated after April 2017 then it has the UCRT. If you go to the Microsoft Update catalogue and look at the details for KB3118401, you will notice that it lists all of the monthly Windows Update packages as superseding The UCRT is deployed through Windows update for versions of Windows prior to Windows 10.
