Apple is rolling out the option to automatically download macOS updates starting with macOS Sierra today. The major Mac software update was released at the end of September, and starting today Apple will begin automatically downloading the update on Macs that haven’t updated yet (via The Loop).
Mac users will still need to manually allow the software update to be installed; the only change here is that the update can download automatically then prompt you to install. You can also opt out of this feature in System Preferences → App Store → Download newly available updates in the background.
The Loop says Apple will not download macOS updates even with this option enabled if you’re Mac runs out of local storage, however, and the automatic download will be deleted if your Mac needs additional storage and you don’t manually delete it first.
Before today, updating to macOS Sierra required manually downloading the installer from the Mac App Store. Today’s change could be seen as a way to encourage adoption or simply as a way to make it easier to stay on the latest software update as new versions become more frequent.