How do I reinstall Catalina without losing data?

Reinstalling macOS Catalina can be necessary if you are experiencing issues with your current installation or want to start fresh with a clean install. However, reinstalling your operating system can be concerning because you don’t want to lose any of your important files or data in the process.

The good news is that it is possible to reinstall Catalina without losing any files, data, or settings. By following some key steps both before and during the reinstallation process, you can safely reinstall Catalina while keeping all your apps, documents, photos, music, and other data intact.

Back Up Your Mac Before Reinstalling Catalina

The most crucial step to take before reinstalling Catalina is to make sure you have a complete and current backup of your Mac. This will allow you to restore all your data after you have reinstalled the OS. Here are some backup options to consider:

  • Time Machine – This built-in macOS backup tool allows you to make a bootable backup of your entire Mac on an external hard drive. Time Machine makes hourly, daily, and weekly backups automatically once configured.
  • Clone your startup disk – Using a third party utility like Carbon Copy Cloner or SuperDuper, you can create a complete bootable duplicate of your current Catalina startup disk on another external drive.
  • Cloud backup – Services like iCloud, Dropbox, Google Drive or OneDrive allow you to backup your files and data to the cloud.
  • Manual backup – You can always manually backup important files by copying them to an external hard drive or cloud storage.

Ideally, you should have both a clone backup as well as a cloud or external drive backup before reinstalling Catalina. This will give you the most complete and redundant coverage to restore from.

How to Reinstall Catalina Without Losing Data

Once you have your Mac completely backed up, you are ready to reinstall Catalina while preserving your data. Here is the process:

  1. Boot to the Catalina installer
  2. Start by booting your Mac to the Catalina installer. This can be done by:

    • Using the bootable installer you made with the Catalina download from the App Store. Hold Option while booting and select the installer drive.
    • Booting to macOS Recovery by holding Command+R during startup, then selecting Reinstall macOS from the utilities window.
    • Booting to an external clone drive you made of your current Catalina system.
  3. Erase and reformat the startup disk
  4. Once booted to the Catalina installer, open Disk Utility from the Utilities menu. Select your current Catalina startup disk and erase it. This will wipe the disk clean without touching other connected drives.

    Make sure to reformat the disk to APFS and GUID partition scheme. This will prep it for a fresh Catalina install.

  5. Install Catalina to the erased startup disk
  6. With your startup disk erased, you can go ahead and install Catalina onto it from the installer drive you booted from.

    Be sure to select the erased startup disk as the destination for installation. The Catalina installer will create all necessary partitions and install a fresh copy of the OS.

  7. Migration Assistant to restore your data
  8. Once Catalina is done installing to your freshly formatted startup disk, you can migrate all your apps, files, and settings from your backup.

    When you reach the desktop for the first time, you will be prompted to migrate from a Time Machine or other disk backup. You can also open Migration Assistant manually to restore from a backup.

    Select your desired backup source and Migration Assistant will copy everything over to your new Catalina install, preserving all your data.

By erasing your startup disk before reinstalling Catalina, you ensure none of the old OS files or settings get carried over. This gives you a completely fresh install. But you maintain all your apps, files, and custom settings by migrating your user data back after installation.

Additional Tips for Reinstalling Catalina

Here are some additional tips to ensure the reinstallation process goes smoothly and safely:

  • Deauthorize iTunes/App Store – Sign out of iTunes and the App Store before erasing your startup disk. This will allow you to reauthorize the apps after restoring.
  • Backup encryption key – If FileVault encryption is enabled, make sure you have the encryption key backed up so you can access encrypted data after restoring.
  • iCloud data – Sign out of iCloud before erasing your startup disk to avoid any conflicts restoring iCloud data later.
  • Drive backups – Disconnect any external backup drives before erasing your startup disk to avoid accidentally deleting those.
  • User accounts – Make sure you know the names of all your user accounts to properly restore them from backup.

Alternative: Erase Volume Group Instead of Whole Disk

There is an alternative method that will erase just your user data instead of the entire startup disk. Here are the steps:

  1. Boot to Recovery
  2. Open Disk Utility
  3. Select the Volume Group underneath your startup disk (usually Macintosh HD)
  4. Click Erase, choosing APFS and GUID
  5. Quit Disk Utility and install Catalina to your startup disk
  6. Restore user data from backup

This preserves the base OS but erases your user account info, apps, and data. You then selectively restore just your user data. This provides a cleaner slate without completely reinstalling the OS.

FAQs About Reinstalling Catalina Without Losing Data

Is it safe to reinstall Catalina?

Yes, reinstalling Catalina is generally safe if you follow the proper steps to back up your data first. Making a complete clone backup of your startup disk prior to reinstalling Catalina will allow you to restore all your data after.

Will reinstalling Catalina delete all my files?

If you erase your entire startup disk before reinstalling Catalina, it will delete everything at first. But you can restore all files and data from a backup after Catalina is freshly installed. Just be sure to fully back up first.

What is the best way to back up my Mac before reinstalling?

The best backup option is creating a bootable duplicate clone of your startup disk using a utility like Carbon Copy Cloner or SuperDuper. This provides a full backup you can boot from and restore from.

How do I restore my apps after reinstalling Catalina?

The Migration Assistant tool will transfer over all your apps when restoring data from a backup after reinstalling Catalina. You can also redownload any purchased apps from the App Store.

Will my settings and preferences be saved when reinstalling?

Yes, user settings, preferences, and configuration files will be preserved when restoring from a backup after reinstalling Catalina. Backup utilities capture your user data.

How can I reinstall Catalina without losing my files?

To reinstall Catalina without losing files, follow these key steps:

  1. Back up your Mac completely with Time Machine or a clone backup
  2. Erase and reformat the Catalina startup disk
  3. Reinstall a fresh copy of Catalina to the erased disk
  4. Use Migration Assistant to import your user data from the backup

This will give you a completely fresh OS install while maintaining all your user data like documents, photos, music, and other files.


Reinstalling Catalina does not have to result in lost files, data, or settings. By properly backing up your Mac before reinstalling the OS, you can maintain all your important user data. After erasing your startup disk and installing a fresh Catalina copy, simply restore your apps, files, settings, and configuration from backup.

Follow the steps outlined here for safe Catalina reinstallation without any data loss. Be sure to use a bootable duplicate clone backup for full system recovery. With a current backup, you can confidently reinstall Catalina knowing you can easily restore all your important documents, media, apps, and configurations.