The Background Bandwidth Drain
By default, macOS is configured to automatically download new system updates (which can easily exceed 10 gigabytes) in the background the moment they become available. While Apple does this to ensure your computer stays secure, these massive hidden downloads can be disastrous if you are working on a metered internet connection, using a mobile hotspot, or simply trying to participate in a video call without your network bandwidth suddenly grinding to a halt.
How to Disable Automatic Update Downloads
You can configure your Mac to check for updates so you know they exist, but explicitly stop it from actually downloading the massive files until you manually give it permission to do so.
1. Click the Apple logo () in the top-left corner of the menu bar.
2. Select System Settings from the drop-down menu (or System Preferences on older versions).
3. In the left-hand sidebar, click on General.
4. In the main pane, click on Software Update.
5. You will see a section labelled “Automatic Updates.” Click the small Information (i) icon on the far right of this line.
6. A new dialogue box will appear with several toggle switches. Locate the setting labelled Download new updates when available.
7. Click the toggle switch to turn it Off.
8. Click Done to save your changes. You may be prompted to enter your Mac administrator password to confirm.
Managing Essential Security Patches
In that same settings menu, you will see another toggle labelled Install Security Responses and system files. It is highly recommended that you leave this specific setting On. Security Responses are incredibly tiny, rapid patches designed to fix critical zero-day vulnerabilities instantly. They will not drain your bandwidth, and leaving them enabled ensures your Mac remains protected from active threats even while you are holding off on the massive, multi-gigabyte feature updates.