Should You Reinstall macOS?
Do you really need to reinstall macOS? That's the first question you should ask yourself. If you're unsure, check the table below to find the best solution for your specific situation.
| Your situation | What to do |
| Mac is running slow | Try troubleshooting first |
| Mac has system errors | Reinstall macOS |
| Mac won't start normally | Start Recovery → Disk Utility → reinstall if needed |
| You want to keep your files | Reinstall without erasing |
| You want to sell your Mac | Erase Mac |
| You want a completely fresh installation | Erase and reinstall macOS |
| Recovery doesn't work | Try alternative installation/recovery methods |
| You want an older macOS | Follow a dedicated downgrade/older macOS guide |
Before Reinstalling macOS
Before reinstalling macOS, you'll need to complete a few preparatory steps:
- Back up your Mac with Time Machine, or an external drive via disk clone
- Connect the Mac to power
- Make sure you have a stable internet connection
- Disconnect unnecessary external devices
- Recall your Mac login password
- If FileVault or other security features are involved, be prepared to authenticate
- If you plan to sell your Mac, use the erase/reset procedure instead of ordinary reinstallation
Can I Reinstall macOS without Losing My Data?
Yes. A normal macOS reinstallation from macOS Recovery is designed to reinstall the operating system without deleting your personal files, apps, or user settings. However, backing up your Mac before performing such a major task on your device is important. You will lose data if you mistakenly operate during the process and don't have a backup.
Therefore, to reinstall macOS without losing data, you'd better back up your Mac first. You can choose multiple ways to back up, like Time Machine and iCloud. If you want to back up all the Mac data quickly, you can consider cloning a Mac hard drive with iBoysoft DiskGeeker for Mac.
How to Reinstall macOS without Erasing
Reinstalling macOS without erasing data is mainly used for:
- macOS system problems
- Corrupted system files
- Startup problems
- macOS behaving abnormally
- Reinstalling the same/current macOS
- Repairing an installation
Step 1. Enter macOS Recovery
You should identify your Mac model first, whether it is an Intel-based Mac or an Apple Silicon Mac, as the ways to enter macOS Recovery mode differ for different Mac models. After that, you can proceed to reinstall macOS from Recovery Mode.
On an Apple Silicon Mac
- Shut down your Mac completely
- Press and hold the power button until Startup Options appears
- Click Options
- Click Continue to boot into macOS Recovery
This method applies to Macs with Apple Silicon, including M1, M2, M3, M4, M5, and later chips.
On an Intel Mac
- Shut down your Mac completely
- Turn it on while holding down the Command + R keys simultaneously
- Release the keys when you see an Apple logo, and your Mac will boot into the macOS Utilities window in the recovery partition.
During the boot up to Recovery Mode, an admin password might be required to authenticate your identity for an OS reinstallation. After you enter the functioning recovery partition, you will see the macOS Utilities window.
Tips: Apart from reinstalling from Recovery Mode, you can also download the macOS installer and then create a bootable USB installer from DMG to reinstall macOS.
If you can't download macOS due to incompatibility, follow: Download macOS on Unsupported Macs
Step 2. Reinstall macOS 27 Golden Gate
I've reinstalled macOS Golden Gate 27.0 on my M1 MacBook Air (2020). If you're running on an Intel-based Mac, you can't reinstall the latest macOS 27 version on your Intel Mac. Find all macOS versions and know which operating system will be downloaded and installed on your machine.
- I clicked the "Reinstall macOS 27 Golden Gate" option and click Continue.
- Click Continue.
- I chose Agree to the terms of the software license agreement.
- I selected Macintosh HD as the destination to reinstall macOS 27. Click Continue then.
- A pop-up message notified me that the target volume I chose didn't have enough space to install. An additional 22.1 GB was required. Macintosh HD is 126.87 GB in total, with 32.18 GB available. That means the macOS 27 reinstallation requires at least 54.28 GB.
I turned to iBoysoft Cleaner to visually analyze my Macintosh HD space and clean up space for the macOS 27 reinstallation by clearing system junk, large files, duplicate files, similar photos, unused apps, app residuals, etc. You can check the how-to guide here if you need to free up space for macOS reinstallation, as well. - After space cleanup, I tapped Continue to begin the reinstallation. I saw a window with a progress bar and time remaining for installing macOS 27.
If you are unable to continue the macOS installation but encounter an error saying "The installer information on the recovery server is damaged," find solutions here.
How to Erase and Reinstall macOS
Erasing data and reinstalling macOS is mainly used for:
- Preparing the Mac for sale
- Completely starting over
- Suspected severe system/storage problems
- Intentionally removing all user data
Note: Before you start, ensure you have backed up any files you want to keep to an external drive. Even though you don't intend to wipe your MacBook, securing your files is a good idea before macOS reinstallation, since it is a major procedure.
Step 1. Enter macOS Recovery Mode
This step is the same as the one described above, so there's no need to repeat it here.
Step 2. Erase Mac
If you want a clean macOS reinstallation, formatting the Mac startup disk is necessary. Before proceeding, make sure you have backed up all your important files to a computer, cloud service or an external storage device.
Here is how I erase my Apple Silicon M1 Mac:
- I opened Disk Utility > chose Macintosh HD volumes
- Clicked the Erase button in the upper menu
- A pop-up message told me that Macintosh HD can't be erased. And it showed up the “Open Transfer or Reset Settings" option for me to safely erase and restore Mac to factory settings
- I tapped that option and I was re-directed to the Transfer or Reset windows under General in Settings
- I clicked "Erase All Content and Settings…". Then it auto-erased contents from my MacBook Air.
Here's how to wipe an older Mac:
- Open Disk Utility.
- On the sidebar of Disk Utility, select the system volume that contains the operating system and click Erase.
- Give a name to the volume you are going to format. It is highly recommended to use "Macintosh HD" for convenience's sake.
- Select APFS file system.
- Click Erase Volume Group. This will delete the Macintosh HD - Data volume, the system created when you upgraded to the new macOS and all other volumes you created as a user. Deleting all the volumes can free up space and eliminate possible conflicts for a clean macOS reinstallation.
- Confirm the Mac wiping by clicking the Erase button.
It will take a few minutes to half an hour to complete the disk formatting. Wait patiently and do not terminate it halfway. When done, quit Disk Utility to return to the macOS Utilities window.
Step 3. Reinstall macOS 27 or 26
The steps are the same as those outlined above. Refer to the previous section for detailed instructions.
Can't reinstall macOS after erasing the Mac? Here's how to fix it.
Extended Info: Reinstall macOS vs Erase Mac
The following table provides a side-by-side comparison of reinstalling macOS and erasing a Mac, helping you quickly understand the key differences at a glance.
| Reinstall macOS | Erase Mac | |
| Reinstall operating system | Yes | Yes |
| Delete personal files | Normally no | Yes |
| Delete apps | Normally no | Yes |
| Keep user settings | Normally yes | No |
| Best for troubleshooting | Yes | Usually not the first choice |
| Best before selling | No | Yes |
| Require backup | Strongly recommended | Essential |
Which Version of macOS Will Reinstall from Recovery?
The steps for reinstalling macOS—whether you want to reinstall your current version, install the latest compatible version, or restore the version that originally came with your Mac—depend on whether your Mac uses Apple Silicon or an Intel processor. Check the following table to select your macOS version:
| Goal | Apple Silicon | Intel |
| Reinstall current/recently installed macOS | macOS Recovery | Command-R |
| Install latest compatible macOS | Use appropriate upgrade/install path | Option-Command-R |
| Reinstall original/closest available macOS | Not applicable in the same Intel shortcut sense. Use a bootable USB installer | Shift-Option-Command-R |
What If macOS Recovery Doesn't Work?
Reinstall macOS not working? There are workarounds.
Unexpectedly, if the Command R not working or the recovery partition is damaged, you can't get into Recovery mode, let alone reinstall the Mac operating system. However, Recovery mode is not the only way that enables you to reinstall macOS, there are some alternative methods you can use when Recovery mode is not working.
Internet recovery mode. It is an Internet-based version of Recovery Mode. Once the Mac fails to boot into macOS Recovery mode, it will automatically enter Internet recovery mode to access the macOS Utilities window. It requires a stable internet connection.
Fallback recovery OS mode. This is a unique feature on Apple Silicon Mac, the second copy of recoveryOS. From a shutdown state on an M1 Mac, press and hold the power button to enter Fallback recovery OS mode.
DFU mode. Unlike the above startup modes, DFU is burned into the hardware as part of SecureROM. It is used to get your device back into a proper, working order. Combined with Apple Configurator 2, it can revive and restore a faulty Mac.
Create a macOS 27 Golden Gate USB installer. If macOS Recovery isn't working, you can create a bootable installer using a USB flash drive and a compatible full macOS installer. Apple currently provides an official createinstallmedia command for macOS 27 Golden Gate.
Generally, you can reinstall macOS using Recovery mode with ease on your Mac computer. If the Recovery mode is not working, we have introduced alternative methods to reinstall macOS in this guide. After the reinstallation, you can enjoy your new Mac.
FAQs
- QWill reinstalling macOS delete my files?
-
A
No, not normally. Reinstalling macOS from Recovery generally preserves your personal files, apps, and user settings. Erasing the Mac is a separate procedure.
- QHow to factory reset a Mac?
-
A
Restart your Mac, hold Command + R to enter Recovery, erase the disk in Disk Utility, then select Reinstall macOS.
- QWhy can't I reinstall my Mac to the latest version?
-
A
It may be due to outdated hardware, limited storage, network issues, or your Mac only supporting its originally shipped macOS.
- QDo I need to erase Macintosh HD before reinstalling macOS?
-
A
Normally you don't unless you want to prepare the Mac for sale or need a clean reinstallation.
- QHow do I reinstall macOS 27 Golden Gate?
-
A
Enter macOS Recovery and follow its instructions to reinstall macOS 27 Golden Gate.