How do I reinstall macOS without losing apps and data?

Reinstalling macOS can help fix software issues and improve system performance, but it can also result in data loss if not done properly. The good news is that you can reinstall macOS without losing your apps, documents, settings, and other files. Here is a step-by-step guide on how to reinstall macOS while preserving your data.


Before starting the reinstallation process, make sure you have the following:

  • A bootable macOS installer. This can be created from the App Store or downloaded directly from Apple.
  • An external storage device. This will be used to store a backup of your data.
  • Your Apple ID and password. This is needed to reinstall macOS and restore data from iCloud.
  • Time. Reinstalling macOS and restoring data can take several hours.

Back Up Your Data

The first step is to create a backup of all your important files, documents, photos, music, and other data. Here are a few options for backing up your data:

Use Time Machine

Time Machine is macOS’ built-in backup utility. It can be used to create backups to an external drive connected to your Mac. Here’s how to use it:

  1. Connect an external HDD or SSD drive to your Mac.
  2. Open System Preferences > Time Machine.
  3. Click Select Backup Disk and choose your external drive.
  4. Turn on Time Machine.
  5. Time Machine will create hourly backups of changed files and a daily backup of the entire system.

Clone your startup disk

You can create an exact replica of your current startup disk using Disk Utility or third-party cloning software like Carbon Copy Cloner. This will replicate everything including your OS, apps, settings and data.

Manually copy files

You can manually copy your important files and folders to an external drive. Make sure to get files from your home folder, Desktop, Documents, Downloads, etc. After copying them, double check to ensure they have been copied properly.

iCloud backup

If you use iCloud, make sure you have a recent backup of your photos, documents, contacts, calendars and other data. You can confirm when your last backup was and start a new manual backup from System Preferences > iCloud.

How to Reinstall macOS Without Losing Data

Once you have backups ready, you can proceed with reinstalling macOS. This involves erasing your startup disk and installing a fresh copy of the OS. Your data will still be preserved in the backups you created.

Restart in Recovery Mode

Follow these steps to boot your Mac into Recovery mode:

  1. Restart your Mac and immediately press and hold Command + R after you hear the startup sound.
  2. This will boot your Mac into Recovery mode. You’ll see the macOS Utilities window.

Erase the startup disk

In the Utilities window:

  1. Select Disk Utility.
  2. Choose your startup disk from the sidebar (usually named Macintosh HD).
  3. Click Erase at the top.
  4. Choose APFS format and GUID partition scheme.
  5. Give the disk a name (Macintosh HD is fine).
  6. Click Erase to confirm.

This will quickly erase your startup disk without touching your backups.

Reinstall macOS

With your startup disk erased, go back to the Utilities window and:

  1. Choose Reinstall macOS.
  2. Follow the prompts to reinstall the latest macOS version.
  3. It will ask you to select a disk – choose your erased startup disk.
  4. The installation will take around 20-30 minutes.

Restore Your Data

Once macOS has been reinstalled, you can restore your data from the backups:

Restore from Time Machine

  1. Open Migration Assistant (located in /Applications/Utilities).
  2. Choose your Time Machine backup and click Continue.
  3. Select the user account to restore (if prompted).
  4. Choose which data to restore – make sure Apps, Settings, Other Files & Folders are checked.
  5. Click Continue and macOS will restore the data.

Restore from clone backup

  1. Reboot from your clone backup disk.
  2. Open Migration Assistant.
  3. Select the startup disk clone as the source.
  4. Choose your account and files to restore.
  5. Let the restore process finish.

Manually restore files

  1. Copy your files/folders back from the external drive to your user account.
  2. Put them back in the appropriate locations on your Mac.

Restore from iCloud

  1. Sign in to iCloud after reinstalling macOS.
  2. Turn on iCloud Drive and ensure Desktop & Documents syncing is enabled.
  3. Go to Photos and turn on iCloud Photo Library.
  4. Your synced iCloud data will download to your Mac.

Reinstall Apps

Your apps will need to be reinstalled after reinstalling macOS. Here are the main ways to get your apps back:

Reinstall from App Store

Any apps you downloaded from the App Store can quickly be reinstalled for free:

  1. Open the App Store app.
  2. Go to the Purchases tab.
  3. Find the app you want to re-download and click the Install button.
  4. Repeat this for all your App Store apps.

Reinstall downloaded apps

For apps you originally downloaded from the web:

  1. Go to the app’s official website.
  2. Download the app again.
  3. Complete the installation process.

Use migration assistant

Migration Assistant can also reinstall your applications from a backup source like Time Machine. Just make sure Apps is checked in the ‘Select data to transfer’ screen.


If you encounter any issues while reinstalling macOS, here are some troubleshooting tips:

Startup disk won’t erase

If Disk Utility won’t let you erase your startup disk, restart into Internet Recovery Mode instead. Then erase disk and reinstall macOS from there.

Can’t reinstall macOS

If the Reinstall macOS option is greyed out in Recovery mode, restart in Internet Recovery again. Or, try using a bootable USB installer to reinstall macOS.

Apps won’t reinstall

Check for any error messages when trying to reinstall apps. For App Store apps, try signing out and back into the App Store first.

Backup restore failed

If Migration Assistant failed to restore your backup, try restoring again from the backup source directly like Time Machine. Data loss is unlikely.

Frequently Asked Questions

Is a clean install better than reinstalling macOS?

A clean install (or erase install) is better if you want to remove all files, settings and start completely fresh. Reinstalling is good if you just want to fix software issues while keeping your data.

Will I lose all my files when reinstalling macOS?

No, you won’t lose any files or data as long as you backup everything first. Just make sure to restore your files after reinstalling macOS.

Do I need internet to reinstall macOS?

An internet connection is required to reinstall macOS and restore data from iCloud. But you can reinstall macOS without internet using a bootable USB installer.

Is reinstalling macOS safe?

Yes, reinstalling macOS is a safe process. As long as you backup your data first, there is minimal risk of data loss when reinstalling.

How can I backup my Mac before reinstalling?

You have a few options to backup your Mac: use Time Machine, create a complete system clone, manually copy important files, or use iCloud Drive and iCloud Photo Library.

What will I lose when erasing my Mac’s disk?

Erasing your startup disk will delete the OS, apps and all files on the system drive. Your data on external drives will not be affected.

Is reinstalling macOS the same as formatting?

No, reinstalling macOS keeps the file system intact while formatting cleans the drive. Reinstalling overwrites just the OS while retaining your files and data.


Reinstalling macOS allows you to start fresh with the operating system without losing your apps and data. By properly backing up your files first and then restoring them afterwards, you can upgrade or troubleshoot macOS while still preserving important documents, settings and applications.

Just make sure to use Time Machine, create a bootable duplicate, or copy important files manually before erasing your startup disk. Test the backups to ensure your data is intact. With a current backup, reinstalling macOS is a safe and straightforward process.