Recovery Mode is possible thanks to the installation of a hidden recovery partition on your Mac’s hard drive and allows the user to perform the aforementioned tasks without needing a macOS DVD or USB installer.
You can let go of the keys when you see a screen similar to the screenshot below. Keep holding as your Mac boots, which may take a few moments depending on its specific configuration. To use Recovery Mode, reboot or start your Mac and hold the Command and R keys simultaneously on your keyboard as you see the iconic white Apple logo against a black screen. Starting with the release of macOS Lion in 2011, Macs have offered a Recovery Mode that users can access to diagnose hardware issues, restore Time Machine backups, manage hard drives, and even reinstall macOS itself.
