There are several reasons why you may want to reinstall the macOS operating system on your Mac, either because the computer is behaving erratically and you think that a clean installation could solve the problem, or simply, to sell your Mac.
You should know that it is even possible to reinstall the original version of macOS with which the Mac once saw, returning to an earlier version with which your computer will surely no longer work.
Regardless of the reason you want to reinstall MacOS, below we show you some of the easiest ways to carry it out, we will show you below one of the easiest ways to do it.
The method is to use the recovery partition, through which, you can reinstall the latest version of macOS installed on your Mac. Because MacOS is installed through the software update (or previously the Mac App Store) it doesn't there are physical installation discs.
For this reason, Apple has made it possible to install the operating system over the Internet using the Recovery HD mode. Another alternative option would be to create a bootable installation on an external drive or pendrive.
If the recovery mode of your Mac does not work, follow the steps in this article on how to reinstall macOS if Recovery does not work.
What do you need to reinstall macOS using Recovery mode?
The first thing is to have a backup. If you plan to clean your Mac by installing the operating system from scratch in order to solve the problems you have, you should know that you are interested in making a previous backup of your most important documents.
The way you do it depends on whether you want to recover your Mac with the same version, or if you want a clean installation. If you use iCloud Drive to synchronize your documents and the cloud desktop, you may not need a backup.
In addition to the Internet connection, if you are using recovery mode, you will need to use a Wi-Fi network with WEP or WPA security. It is something that most domestic wireless networks do, but if you are in a proxy or PPPoE network, then you will have problems.
How to reinstall macOS through Recovery mode
Follow these steps to reinstall the latest version of macOS:
- Start your Mac by pressing and holding the Command + R keys until you hear the start bell and see the earth spinning or the Apple logo.
- A macOS Utilities window opens. The next step depends on whether you want to clean the Mac before reinstalling the operating system, or if you want to clean your disk. Click Disk Utility or go to step 8.
- Once Disk Utility is selected, click Continue.
- Now select the volume you want to erase. You may have to click View> Show all units before viewing the volume. Keep in mind that the process here is slightly different if you are running macOS Catalina. If Catalina is running, there will be two volumes called Macintosh HD and Macintosh HD-Data. You need to erase the Data volume first and then the Macintosh HD. If it doesn't work with Catalina, then you just need to erase the Macintosh HD volume.
- The next step also depends on the version of macOS you are running. In Mojave and Catalina, and potentially in High Sierra (depending on your Mac) be APFS. But on Mac with older versions of macOS, the format must be set to Mac OS Extended (Journaled). You need to have the GUID Partition Table selected as Scheme.
- Click on Erase and wait. (There are functions to erase the disc safely).
- Now choose Disk Utility> Exit Disk Utility. Or simply click on Command + Q.
- Vers the utilities screen again, choose Reinstall macOS.
- After clicking Reinstall macOS, click Continue.
- Enter your Apple ID if necessary and wait while reinstalling MacOS. Wait for this to take a while.
- When the setup wizard starts, leave at this point if you intend to sell your Mac or transfer it to someone familiar so that the next owner can enter their own data. Otherwise, continue setting it up.
How to install an old version of macOS using Recovery mode
In addition to the Command + R key combination mentioned above, there are a couple of more key combinations that you can use to reinstall macOS using recovery mode.
These will allow you to choose between installing the latest version of macOS compatible with your Mac, or go back to the version of macOS that was initially marketed with your Mac.
You can choose between them:
- Command + R install the last version installed on your Mac. Do not update to the last version.
- Option / Alt + Command + R will update you to the latest version of macOS compatible with your Mac. Note: If you are not running Sierra 10.12.4 or later, this will install the version that comes with your Mac; If your Mac has a T2 chip, with Option / Alt + Command + R you will install the latest version of macOS on your Mac.
- Shift + Option / Alt + Command R (if you are running Sierra 10.12.4 or later) install the MacOS version that comes with your Mac, or the closest available.
Follow the steps in the previous section to reinstall MacOS through Recovery.
How to connect to the Internet on macOS with Recovery mode
To reinstall MacOS using recovery mode, you must have an Internet connection. Follow these steps to connect to the Internet in recovery mode if your Mac does not connect automatically:
- Click on the Wi-Fi menu in the upper right corner of the screen.
- Select the Wi-Fi network you wish to use.
- Enter the password if necessary.
The Recovery mode must now be connected to the Internet in order to download the macOS installation software.
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