Backups & restore points · Where backups go
Do backups to an external drive need an internet connection?
Short answer: No. Drive and folder backups run entirely on your Mac and work offline. Only cloud destinations need a connection, and they catch up once you're back online.
No. Backups to a drive or folder run entirely on your Mac, so they work offline — on a plane, with Wi-Fi off, anywhere. Only cloud destinations need a connection, and the network conditions such as Not on a personal hotspot apply to those alone.
If a cloud set is offline, it waits and catches up once you're connected again.