The Silent Gigabytes
macOS is designed to keep your system secure and up-to-date with minimal user friction. By default, the operating system is configured to automatically check for new system updates and, more importantly, silently download these massive files (often several gigabytes in size) in the background. While this ensures your Mac is ready to install the update the moment you click “Restart,” it can be a massive problem if you are working on a strictly metered cellular data connection, tethered to your iPhone, or operating with very little free hard drive space.
Halting the Background Downloads
To preserve your bandwidth and storage space and stop macOS from automatically downloading large system updates without your permission, you must adjust the advanced software update settings.
Click the Apple logo in the extreme top-left corner of your screen and select System Settings. In the left-hand navigation sidebar, scroll down and click on General. In the main right-hand panel, click on Software Update. Look for the line that says “Automatic Updates” and click the small circular “i” (Information) button next to it. A new dialogue box will appear with several specific toggle switches. To stop the massive file transfers, you must find the toggle labelled Download new updates when available and click it to turn it Off. (You can leave “Check for updates” on so you are notified, but the Mac will no longer download the payload until you explicitly click the “Download” button).