The Intrusive Alert
macOS includes a proactive storage management system designed to warn you when a drive is running out of free space. While this is helpful for your primary startup disk (where macOS needs space for swap files and system operations), it can become incredibly annoying when applied to external backup drives, SD cards, or archival storage that you intentionally keep full. The operating system will repeatedly trigger a “Your disk is almost full” banner notification, interrupting your workflow even if the external drive is not required for system stability.
Modifying the System Defaults
Unfortunately, Apple does not provide a standard System Settings toggle to disable this warning on a per-drive basis. To silence the notification, you must modify a hidden system preference using the Terminal application. Open Terminal (found in Applications > Utilities) and prepare to write a new default setting for the macOS disk management daemon.
Type the following command exactly: defaults write com.apple.diskspaced minFreeSpace -int 0 and press Enter. This command instructs the disk space monitor to set the minimum free space threshold to zero, effectively neutralizing the trigger that causes the warning to appear. You must log out of your Mac and log back in (or restart your computer) for the daemon to load the new preference. The low space warnings will immediately cease across all connected volumes.