The Constant Backup Question
Time Machine is Apple’s robust, built-in backup solution for macOS. Because regular backups are critical for data safety, macOS is incredibly aggressive in promoting the feature. Whenever you plug a brand new external hard drive, USB flash drive, or SD card into your Mac, the operating system instantly detects it and throws a pop-up window asking, “Do you want to use [Drive Name] to back up with Time Machine?” If you are a video editor frequently swapping out external drives to transfer footage, or an IT worker preparing dozens of USB drives, dismissing this prompt multiple times a day is incredibly tedious.
Silencing the Drive Discovery
To stop macOS from automatically asking to configure every new drive as a backup disk and completely disable the Time Machine prompt, you must use a specific command within the Terminal application.
Apple no longer provides a simple graphical checkbox to disable this behavior in System Settings. You must modify the underlying defaults. Open Finder, navigate to Applications, then Utilities, and double-click Terminal to launch it. In the Terminal window, type the following command exactly as written: defaults write com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool true and press Enter. The command will execute silently without providing a confirmation message. Once entered, you can close the Terminal. From now on, whenever you plug in a new external drive, it will simply mount quietly on your desktop or in Finder without triggering the intrusive Time Machine setup prompt.