How can I find what swcdn is trying to download?
Apple documentation describes these hosts as follows:
Network access to the following hostnames are required for installing, restoring, and updating macOS, iOS, and tvOS:




Hosts
Ports
Protocol
OS
Description




mesu.apple.com
443, 80
TCP
iOS, tvOS and macOS
Hosts software update catalog


swcdn.apple.com
80
TCP
macOS only
macOS updates




So this should be about updating OS. If you unselected &quot;Automatically keep my Mac up to date&quot; you should also click on &quot;Advanced&quot; and check what is selected. On my machine, when I unselected automatic updates then under Advanced there were still following options selected: &quot;Check for updates&quot;, &quot;Download new updates when available&quot; and &quot;Install system data files and security updates&quot;.