Summary: This page is about how to reinstall macOS in macOS Recovery mode. Based on if you want to keep the original data on the startup disk, you can either choose to clean reinstall macOS or to reinstall macOS without data loss.

Reinstalling macOS gives your Mac a fresh start especially when you are frequently bothered by some issues, such as Mac not turning on, Mac hanging on the beach ball, apps frozen on your Mac, slow performance, or pink screen on Mac. Most of the time, such issue results from some system-level problems, while reinstalling macOS can easily save your life.

First I clean (erased) the Hard Drive (actually internal ssd). Then tried to do the 'reinstall'. Since the HD was completely. Wiped, I had to do an Internet reinstall. I was stopped in my tracks with the message 'Can't download the additional. Components needed to install Mac OS X'. Some people had trouble with Internet connections in this. I went to the Apple store today and they mentioned I should just try to re-install macOS. I can see the answers suggested here on how to accomplish that: Mac stuck in restart cycle after failed macOS Catalina update. However, when trying to recover / reinstall macOS - the installer also tells me - you don’t have enough free space to reinstall. To reinstall macOS, including the latest Big Sur, Catalina, Mojave, without losing data, you can follow the professional guide to update the OS, which will not cause data loss in most of the case. If you still have worries, back up your Mac in advance or recover the lost files with EaseUS Data Recovery Wizard.

Close all open apps. The Catalina installer can be run directly from your current Mac startup drive when you perform a clean install on a non-startup drive. Launch the macOS Catalina installer app located in the /Applications folder. It will have a name similar to: Install macOS Catalina. The installer will open. Reinstall your computer’s original version of macOS (including available updates): Press and hold Shift-Option-Command-R. Reinstall the version of macOS stored on your computer’s built-in recovery volume: Press and hold Command-R. In the Recovery app window, select Reinstall macOS Big Sur, then click Continue. Follow the onscreen instructions.

• How to reinstall macOS on an M1 Mac?

How to reinstall macOS from macOS Recovery mode?

When you need to reinstall macOS on your Mac, macOS Recovery mode makes this process easy and quick. By the way, if you want to learn more about macOS Recovery mode, you can watch this video.

To reinstall macOS in macOS Recovery mode:

Step 1: Make sure your Mac is connected to a stable Internet within all the following steps.

Step 2: Identify it's an Intel or M1 Mac, and immediately do one of the followings.

• Press and hold Command + Option + R.This allows you to reinstall the latest version of macOS that is compatible with your Mac computer from the internet.
• Press and hold Shift + Command + Option + R. This option allows you to reinstall the macOS that came with your Mac, or the closest version still available.
• Press and hold Command + R. This allows you to reinstall the version of macOS stored on your built-in recovery disk, including any updates that you installed.

• How to Boot into & Use M1 Mac Recovery Mode

Step 3: Release these keys when you see an Apple logo, spinning globe, or the Utilities window.

Step 4: Enter the requested password if you are prompted to enter a firmware password or the administrator's login password.

• Recover/reset your forgotten Mac password

• Mac won't accept correct password, what to do?

Step 5: Decide if you want to clean install the system, or just reinstall macOS without losing your original data.

If you want to factory reset the Mac for selling or giveaway, or the startup disk becomes corrupted, you might want to erase the startup disk before reinstallation. This guarantees a fresh and clean installation as it wipes all your personal data on the disk.

• How to factory reset your Mac?

• How to reset your M1 Mac to factory settings?

If you only want to reinstall macOS because the original operating system is not working as you expect, you might want to keep your personal data intact. In case files are deleted or lost by accident during macOS reinstallation, you should have a backup of your data or getting files off first.

• How to get files off a MacBook that won't turn on?

Step 6: Either after erasing the startup disk or getting files off the Mac, you can then go back to macOS Utilities and choose Reinstall macOS. Check this post to find all macOS versions and know which one you are going to reinstall.

Step 7: Follow the on-screen instructions and choose a disk to reinstall the OS.

• If the internal startup disk is not showing up, or the installer says that it can't install macOS on your computer or volume, you might need to back up files and then erase your disk.
• If the installer asks you to choose Macintosh HD or Macintosh HD - Data when installing macOS Catalina, choose Macintosh HD.

Other ways to install macOS

Apart from reinstalling macOS from macOS Recovery mode, you have other options according to your situations.

1. Get released macOS versions or updates by App Store or Software Update preferences.
2. Get macOS beta (such as macOS Monterey that might be buggy now) through Apple’s developer website.

Whatever your situation of reinstalling macOS is, you should always retrieve your data from the Mac before any further movement. After all, you can't tell if you want it back or not in the future.

How to access and use the Internet Recovery mode on Mac computers?

Apple computers are well-known as stable devices with good performance and hardware specifications. The Mac operating system also includes various self-diagnosis and repair tools. Bear in mind, however, that these features might be susceptible to failure. When built-in tools or software-based solutions do not work, the last and most efficient solution is to reinstall the operating system. All modern Mac computers contain two separate methods to reinstall the operating system (by 'reinstall', we mean installation of a fresh OS X version). You can choose to install the operating system from a startup disk or via Internet Recovery.

In this article, we describe the second method: Internet Recovery to install the operating system version that came with the version of your computer. If your computer was released with OS X Mavericks, using Internet Recovery will install this particular version, while reinstallation from the recovery partition will result in a fresh version of the current operating system. Therefore, if you perform the reinstallation process via the Recovery utility, you will receive the same operating system version that existed prior to reinstallation. The Internet Recovery method is useful if you wish to downgrade the operating system. A big advantage of this method is the ability to bring back the computer to full functionality when software is corrupted. Note, however, that stable internet access is required to perform the reinstallation process via Internet Recovery. An unstable Internet connection can lead to the process crashing and no access to the computer. Therefore, you are advised to use an Ethernet network, rather than Wi-Fi. In this article, we walk through the entire Internet Recovery method.

Table of Contents:

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Requirements to access Internet Recovery Mode

Ensure that the Mac meets the minimum requirements to access Internet Recovery mode. All compatible computers are listed below. Bear in mind that some earlier versions of Apple devices might also use this feature. Apple state that Firmware updates grant access to Internet Recovery mode. If your device is older than the machines listed below, check the Apple firmware updates list here.

• MacBook Pro (13-inch, Early 2011)
• MacBook Pro (15-inch, Early 2011)
• MacBook Pro (17-inch, Early 2011)
• iMac (21.5-inch, Mid 2011)
• iMac (27-inch, Mid 2011)
• MacBook (13-inch, Mid 2010)
• MacBook Pro (13-inch, Mid 2010)
• Mac mini (Mid 2010)
• MacBook Pro (15-inch and 17-inch, Mid 2010)
• iMac (21.5-inch and 27-inch, Mid 2010)
• MacBook Air (11-inch and 13-inch, Late 2010)

If you wish to reinstall the Mac operating system, your network must use DHCP and WPA/WPA security methods. All authentication methods listed below are incompatible with macOS installation via Internet Recovery. If your network uses one of the methods listed, change the setting to a compatible configuration (at least for the purpose of the installation process).

• WEP
• WPA-Enterprise
• Certificate-based authentication / 802.1x
• Proxies (where specific proxy servers must be configured in network preferences)
• Captive Wi-Fi networks (where you click an “Agree” button to access the Internet)
• PPPoE (where there is no router handling the PPPoE connection)

Reinstall operating system by using Internet Recovery mode

When you are sure that the Mac is able to access Internet Recovery mode, there is another important task before installing the fresh operating system version. After a successful reinstallation process, the computer will contain only the default software (which is delivered with macOS). All personal data and applications that you have manually applied to the hard disk will be erased. To protect your personal data, create a backup with Time Machine or similar software. Finally, when you are ready to reinstall the operating system, click the Apple logo in the menu bar at top of the screen and select Restart or Shut Down. Once the system starts booting and you hear the startup chime, hold down the combination of Command, Option (Alt), and R.

Keep holding these keys until the animated globe appears with the message below stating 'Starting Internet Recovery' and 'This may take a while'. Note: If you are using a Mac laptop, use the built-in keyboard to access Internet Recovery Mode, since keystrokes might not register properly on external keyboards.

How To Erase And Reinstall Macos Catalina

Next, select the Wi-Fi network. If you are not using an Ethernet network, click the drop-down menu and select the desired network. You must confirm access to a Wi-Fi network by entering the password. Then press Return on the keyboard or click the checkmark symbol on the screen to continue.

After successful authentication to achieve the network connection, the Mac will begin to download a recovery system image from Apple's servers. You will see a progress bar monitoring the status of the download. Depending on your internet connection, this process may take some time. Ensure that the computer is connected to the power adapter.

Mac Catalina Install Brew

When the image is downloaded, the OS Utilities window will pop-up, giving access to the usual features, such as Restore from Time Machine Backup, Reinstall OS X, Get help online, and Disk Utility. From this point, the process will be similar to the reinstallation via recovery partition. Detailed information about how to install the macOS can be found in this article.