Offline mode in WuMgr uses the wsusscn2.cab catalog from Microsoft to determine required patches. It's called offline because the scanning does not use Windows Update. Downloading the catalog and updates still requires being online, however. Advantage: Will probably work even if Windows Update is slightly out of order. Disadvantage: Does only contain B releases, not Previews. Edit: Check out the meaning of the box "Download and update manually". This might be more like what you desire.