Reinstall Mojave From Catalina

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  1. If you happen to be using Disk Utility on Mojave or an older macOS edition, you can click Mount to make the hidden Data volume appear on the desktop as a separate volume. NOTE: Be advised that you are wholeheartedly discouraged from deleting one of the volumes in Disk Utility unless you’re really feeling irresistible urge to reinstall Catalina.
  2. Lisa, your Mac probably became slow after you upgraded to 10.14 Mojave or Catalina, from 10.13 (High Sierra) or earlier. The reason for it to have become slower is that the upgrade converted your disks from HFS to APFS format. If you are still using hard disks instead of SSDs, then APFS has made them slower, by at least a factor of 2.
Make your Mac invincible

Primary Steps to Wiping a Macintosh Hard Drive Running Catalina. These are the main steps to wiping your data from the computer. First you’ll be removing your Apple ID, then wiping security settings like your fingerprint ID. Then you’ll erase the drive and reinstall macOS. The entire process takes 1-2 hours.

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You took the risk, you tried it, didn’t work for you. That’s fine. If you tried the official version of Catalina — with every feature refined and perfected — and didn’t like it, don’t hesitate to roll back to Mojave.

The new macOS 10.15 Catalina has been released in October 2019. The Apple community is pretty excited about all the bells and whistles Catalina is bringing along. The new shape of iTunes, porting iOS apps to macOS, and an extended workspace with the Sidecar feature seem pretty amazing.

Downgrade from Catalina with Setapp

macOS Catalina not working for you? Get Setapp, a package with Mac apps that help you run a smooth downgrade on a current macOS.

You can check the full list of macOS 10.15 features here.

Importantly, macOS Catalina is the first operating system that won’t be supporting 32-bit apps. So once you upgrade, all of them will cease working automatically. The good news is, Apple warned developers about the update before the release of macOS Mojave, which means they had plenty of time to get prepared. It’s very possible that not every app gets an upgrade before the release, though. If it happens, and you can’t fix the problem, downgrading can be the only solution.

Here’s how you get macOS Mojave back, painlessly.

Step 1. Get a backup

Unless you’ve installed Catalina on a partition — alongside Mojave — there’s no way to keep both. To restore your previous macOS, Catalina has to go away. And with it, all the data you’ve acquired since installing the new macOS 10.15. By backing up your Mac before downgrading, you can keep every single file.

Back up data before downgrading

Download Get Backup Pro, a one-stop tool for creating bootable macOS backups. Whenever you want to roll back to Mojave, take your data with you.

There are multiple ways to backup your Catalina content. You can get an external drive, use a cloud service such as Dropbox, iCloud, and OneDrive, or go with a backup app. The native Time Machine will do the job — not if you need a bootable backup, though. This is why we recommend to get a more solid solution like Get Backup Pro:

  1. Click the plus button at the bottom of the list and name your backup project.
  2. Select a backup destination and whether you want to save original files or a disk image.
  3. Move the files and/or folders to the list and start backing up.

Step 2. Install macOS Mojave on a bootable drive

Basically, you have to go through the ordinary process of installing macOS Mojave from scratch. Go to the Mac App Store and download macOS Mojave. Note that you’ll only be able to directly download the installer before the official release of Catalina. To keep Mojave, you need to install it on a bootable drive.

First, format your disk drive:

  1. Connect an external drive with minimum 8GB of free space via USB.
  2. Open Finder > Applications.
  3. Find Utilities on the list and select Disk Utility.
  4. Find your drive on the list and click Erase.
  5. If you have more than one external hard drive, make sure to name it — you’ll avoid the confusion when creating a bootable drive.
  6. Choose the format from the list (APFS or MacOS Extended (Journaled) if your Mac is using HFS+).
  7. Click Erase.

Next, you’ll need to prepare your drive for Mojave installation:

  1. Open Finder > Applications.
  2. Navigate to Utilities and select Terminal.
  3. Enter the following text into Terminal:
    sudo/Applications/InstallmacOSHighSierra.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install macOS High Sierra.app
  4. In case you’ve changed the name of your drive and it’s not called “Untitled,” make sure you change it in the command above.
  5. Click Enter/Return.
  6. Enter your admin password and click Y to confirm you want to erase the disk.
  7. Click Return. Once the process is completed, you’ll see “Done” in the Terminal window.

Step 3. Let macOS Catalina go

Now you’re ready to get rid of the macOS Catalina beta. With a bootable backup, none of your personal data is at risk.

  1. Click on the Apple icon and select Restart from the drop-down menu.
  2. Reboot your Mac by holding down Command + R.
  3. Select Disk Utility > Continue.
  4. Click on your Startup Disk, and select Erase.
  5. Enter the name of what should be removed (macOS Catalina).
  6. Select APFS or Mac OS Extended (Journaled) and click Erase.

Step 4. Welcome macOS Mojave, again

Maybe your Mac came to you with macOS Mojave. If that’s the case, reinstalling is pretty easy. Reboot your computer by holding down Shift + Option + Command + R, and you’re good to go. Otherwise, here’s the instruction on how to get Mojave back:

  1. Check your internet connection and make sure it’s stable.
  2. Restart the system and hold Option.
  3. Select your bootable drive with macOS Mojave from the startup disk list.
  4. Hit Continue and wait for the new macOS (or should we call it old?) to finish installing.

Step 5. Restore your backup files

With macOS Mojave reinstalled, you can get your hands on the Catalina settings you’ve saved with a recent backup. You can choose the tool you used to backup your disk at the beginning — both Time Machine and Get Backup Pro will work.

If you used Get Backup Pro, open the Clone tab to find a Catalina backup there. Choose the destination and click on the Start button. As easy as that.

To recover Catalina files from a Time Machine backup, do the following:

  1. After checking the internet connection, choose to restart your system in the Apple menu.
  2. Enter the Recovery Mode (Command + R).
  3. Navigate to Utilities and click Restore from Time Machine Backup > Continue.
  4. Select the backup source > Continue.
  5. Click on your backup > Continue.

Once Time Machine will restore the files, your Mac will reboot. It could take a while. But that’s all it takes to get your Mac up and running — with macOS Mojave and all of your Catalina data.

Even though Catalina imperfections are something we can’t ignore, we encourage you to give macOS Catalina a try. It’s pretty solid and beats Mojave in many functionality aspects. After all, you have nothing to lose. With a few Setapp apps like Get Backup Pro for backups and CleanMyMac X for keeping your Mac tidy, you can handle the upgrade. Even if you decide to go back eventually.

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If you have installed Big Sur, Catalina, Mojave or earlier versions, you may have to reinstall macOS for following reasons:

  • Reinstall When There is New macOS Version Available

Apple keeps working constantly to fix bugs, make performance tweaks, add new features or enhance coding. Therefore, doubtless, there will be new versions of macOS available to upgrade and reinstall.

  • Your Mac is Running Slow

As we all know, for no specific reason, system reinstallation can magically solve a slow Mac in most cases.

  • Your System Keeps Crashing or Works Improperly

When you continuously see error messages appear on your mac, or your programs randomly crash/freeze for no reason, like FaceTime won't work, Contacts or Calendar shows a delay or mess, blue teeth or WiFi won't connect…Then, you have a good reason to reinstall macOS.

  • You are Going to Sell the Mac

In the case that you want to sell your mac, besides erasing all your personal data and traces on the mac, you will need to reinstall macOS as well.

It is not complicate to reinstall macOS Big Sur or Catalina, but if you want to reinstall macOS without losing data, there are 3 steps you must follow.

Recover Files after macOS Reinstall

  • Recover data lost due to macOS reinstallation, upgrade, downgrade
  • Recover data lost due to accident deletion, formatting, etc.
  • Restore data from both internal and external storage device
  • Recover videos, audios, images, documents, and other 200+ files
  • 5 recovery modes to find files back easily
  • High recovery rate
  • Support Big Sur, Catalina, Mojave and earlier
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3 Steps to Reinstall macOS Big Sur or Catalina without Losing Data

We all save tons of data on our Mac, so when we decide to reinstall macOS Big Sur/Catalina, the top concern always goes to “will I lost everything if I reinstall macOS”. In fact, reinstallation of macOS doesn’t necessarily cause lost data, it just create a new copy, your existing files and data saved in programs won't be altered or deleted. But just in case of bad luck, we need to do some work on BACKUP, this is crucial for macOS reinstallation without losing data.

Step 1. Prepare Your Mac for Reinstallation.

  • Make enough room for Big Sur or Catalina reinstallation, at least 36GB, so the reinstallation process won't pause or stopped for insufficient space.
  • Also, quit all apps or programs under work, so your Mac is fully geared to reinstall.
  • Check drive conditions. Open Disk Utility and perform the Frist Aid on your hard drive where to reinstall the macOS to make sure your drive is in good condition for reinstallation.

Step 2. Backup All Your Files for macOS Install (Crucial)

Backup is an indispensable step involved in the macOS reinstallation, here are several options to backup your data.

Reinstall

Option One: Using Time Machine

  1. Go to Finder>Application, launch Time Machine and choose “Set Up Time Machine”.
  2. Click “Select Backup Disk” to choose an external hard drive to back up the files.
  3. Then Check the box before “Back Up Automatically”. Also, you can adjust the backup setting in menu “Options”.

If this is the first time you use Time Machine to backup, wait patiently for Time Machine to complete the backup, it will prompt the notification once finishes.

Option Two: Using Hard Drive

  1. Connect your hard drive to Mac.
  2. Open Finder to check if your hard drive is present under “Devices”.
  3. Create a new folder, copy and paste or directly move the items you want to save from Mac to this folder.
  4. Finally, eject your hard drive.

Option Three: Using iCloud Service (Backup Desk and Documents Folders)

  1. Go to Finder>System Preference, click on “iCloud” to bring up its main interface.
  2. Click the “Options” button for “iCloud”, and check the box before “Desktop and Documents Folders”, then click on “Done”.

Most of our mac users prefer to backup all files but apps. So, to save you from troubles of lost data due to macOS reinstallation, you are recommended to keep records of what apps you have installed, the account and password, also, you can take screenshots of the settings.

Step 3. Reinstall macOS Big Sur or Catalina without Losing Data.

Option #1: Reinstall macOS without Losing Data From Internet Recovery

  1. Click the Apple icon>Restart.
  2. Hold down the key combination: Command+R, you will see the Apple logo.
  3. Then choose “Reinstall macOS Big Sur” from utilities window and click “Continue”.
  4. Select your hard drive, click “Install” and wait for end of reinstallation.

Option #2 Reinstall macOS without Losing Data From USB

Reinstall Mojave After Catalina

  1. Download the macOS Big Sur install from Mac App Store onto your Mac;
  2. Then connect the USB flash drive to your Mac;
  3. Open Disk Utility program on your Mac, choose the USB flash drive and click Erase to have a clean drive for the reinstallation;
  4. Open Terminal, copy and paste sudo /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia;
  5. Then add the volume of usb flash drive: --volume /Volumes/MyVolume, replace MyVolume with your usb flash drive name, mine is Untitled;
  6. Press Enter, input password and wait for the process to finish;
  7. Quit Terminal, restart your Mac, hold Command+R when starting Mac until you see the apple logo;
  8. Login into your Mac with password, go to the menu bar>Utilities>Startup Security Utility, enter password again;
  9. Choose Medium Security under Secure Boot and allow booting from external media;
  10. Restart your Mac, in the same time, hold the Option key;
  11. Choose Install macOS Big Sur, click Next and input password, choose Install macOS, continue to finish mac reinstallation from usb.

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What if You Lost Data After macOS Big Sur Reinstallation?

However, losing data after reinstallation still happens. It may result from a interrupted installation (power-off/poor internet connection), corrupt setup, insufficient space or improper actions. Then, what to do if you lost data after reinstallation? Here are 2 methods.

Method 1: Use Cisdem Data Recovery to Recover Data

In the case you didn’t do backup before reinstallation, you will need a dedication data recovery program to find the lost data for you.

Here we recommend Cisdem Data Recovery, a powerful mac program allowing users to recover lost/deleted/corrupted/formatted files from a wide range of external or internal storage devices, no matter the file is lost due to human errors, power-off, reinstallation, upgrade, virus attack or disk crash.

Main Features of Cisdem Data Recovery

  • Recover files lost due to OS reinstallation, upgrade, downgrade;
  • Recover deleted, formatted and lost files;
  • Restore files from internal and external hard drive, USB, SD Card, flash drive, etc.;
  • Restore videos, audios, images, documents, archives, 200+ types;
  • 5 recovery modes: Basic, External Drive, Formatted Drive, Trash, Advanced;
  • Preview files before recovery;
  • Fast scanning and recovery;

Steps to Recover Lost Data after MacOS Reinstallation

Can I Reinstall Mojave From Catalina

  1. Download and install Cisdem Data Recovery on Mac.
    Free Download
  2. Choose a Recovery Mode according to your need.
    If you want an efficient recovery, choose “Basic Data Recovery”, if you want to recover files with a higher success rate, try “Advanced Data Recovery”.
  3. Select the hard drive where you originally stored the files on mac. Then click “Scan”.
  4. Check and preview files found by Cisdem Data Recovery.
  5. Select files to recover.
    Check the box before files that you want to recover, then click “Recover” to find back the lost data caused by reinstallation.

Method 2: Use Time Machine to Recover Data with Backup

If you have backed up your files on mac, you can use Time Machine to restore the lost data.

  • Step1. Go to Finder>Applications>Time Machine, launch it and choose “Enter Time Machine”.
  • Step2. In the popped-up window, use the arrows and timeline to browse the local snapshots and backups.
  • Step3. Find the deleted files, then click “Restore” to recover the lost data caused by reinstallation.

Conclusion

The key to reinstall mac OS Big Sur, Catalina or Mojave without losing data is the backup, since no one can guarantee all data will be perfectly maintained after macOS reinstallation. However, if we unfortunately lost files after macOS reinstallation, Time Machine or Cisdem Data Recovery is helpful to recover them back.

So, do you have any other tips to reinstall macOS without losing data? Please share with more of our mac users.