Time Machine is Apple’s incredibly reliable, built-in backup solution. Because Apple wants to encourage all users to back up their data, macOS is programmed to be highly aggressive whenever it detects new external storage. By default, every single time you plug a brand new external hard drive or high-capacity flash drive into your Mac, a pop-up window will appear asking: “Do you want to use [Drive Name] to back up with Time Machine?”
If you are a video editor swapping shuttle drives all day, or if you simply bought a new external SSD to store your Steam library, this constant prompting quickly becomes an annoyance. You have to manually click “Don’t Use” every single time.
If you already have a dedicated backup drive configured (or if you prefer a third-party backup solution like Carbon Copy Cloner), you can permanently disable this nagging prompt.
How to Disable the New Disk Prompt via Terminal
While older versions of macOS had a simple checkbox for this in the Time Machine System Preferences, modern versions of macOS (Monterey, Ventura, Sonoma) require a quick Terminal command to disable the prompt.
- Open the Terminal app (you can find it in Applications > Utilities, or by searching for it via Spotlight).
- Copy and paste the following command exactly as written:
defaults write com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool true
- Press Enter.
There is no confirmation message, but the change takes effect immediately. You do not even need to restart your Mac. From now on, whenever you plug in a new, unformatted drive, it will simply mount silently to your desktop or Finder sidebar, ready for you to use it exactly how you want.
How to Re-Enable the Prompt
If you ever buy a new Mac or decide you want macOS to remind you to set up backups again, you can easily reverse the command by changing the “true” to “false”:
defaults write com.apple.TimeMachine DoNotOfferNewDisksForBackup -bool false