Most users use the key combination Command (⌘) -R to start Mac in "Recovery Mode". In "macOS Recovery" mode users have access to utility applications as well disk Utility, Port and to the module installation / reinstalling the macOS operating system.
Few know I can use it two other key combinations for entering macOS Recovery. These combinations help users choose another version of the macOS operating system. For example, if you have installed macOS Catalina in beta and you want to go back to macOS Mojave, the key combination Command (⌘) -R, will not help you much.
Command (⌘) -R will reinstall the latest version of macOS previously present on the Mac. That is, if you have macOS Catalina, in macOS Recovery you will find the same version available for reinstallation.
If you hold down the key combination Option-Command (⌘) -R when starting Mac, it will automatically enter "Internet Recovery”And will provide the latest final version of macOS available for your device Requires internet connection and a waiting time until the installation image is downloaded. In our scenario, entering macOS Recovery with the key combination Option-Command (⌘) -R install macOS Mojave. This is the final macOS version at the moment of our tutorial.
For the nostalgic, there is also the key combination Shift-Option-Command (⌘) -R. With this key combination, it will enter into "Internet Recovery" and it will be provided the version of macOS that came with your device. Basically the operating system available on the device in the moment it was removed from the box. An 13-inch MacBook Pro (Mid. 2012) was provided to us OS X Mountain Lion. If you have a very old Mac, the operating system may no longer be available, and in this case, Shift-Option-⌘-R will install the oldest version available.
A brief recap. On Mac we have three "Recovery Mode" variants, each offering the possibility to install a certain version of macOS.
- Command (⌘) -R - reinstall the version of macOS previously present on macOS.
- Option-Command (⌘) -R - installs the latest final version of macOS (requires internet connection)
- Shift-Option-Command (⌘) -R - install the macOS version that came with Mac. If this is no longer available, the following version will be installed. Internet connection is required.
Before you reinstall macOS, it is good to back up all the data stored on it and format the disk or installation partition using Disk Utility.
macOS Recovery - 3 types of OS reinstall on Mac