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

• How To Install Catalina On Mac Mini
• How To Install Catalina On Macbook Air
• How To Erase And Reinstall Macos Catalina
• How To Reinstall Catalina On Macbook Pro

When Disk Utility has finished erasing the disk, quit it to return to the macOS Utilities screen. Choose Install macOS. Press Continue and choose the drive you just erased and re-formatted as the destination. MacOS Catalina will start to install. When it’s finished, your Mac will restart and it will look like a brand new Mac. This video will show you how to do a Clean Install Mac OS Catalina. You can do a clean install from USB drive which we showed you how to build in a previous.

• 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.

How To Install Catalina On Mac Mini

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

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.

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

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.

Mac Won't Turn on after Update to macOS Big Sur?

Here are 10 solutions to fix 'Mac won't turn on after update to macOS Big Sur, Catalina or other versions'.

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

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.

Can you install macOS Catalina on an external SSD connected to your Mac? Yes, it's definitely possible. However, since Apple initiated a relatively new partition scheme (APFS) with macOS High Sierra, the process is slightly different than with older versions of macOS. This article shows you how to set up a new SSD with macOS Catalina that you can boot from.

Why Installing macOS Catalina on External SSD?

macOS can be installed on an external storage device by default, such as HDD, SSD or USB flash drive. And this priciple also applies to macOS Catalina. For permance consideration, external SSD is much better becaus of faster reading and writing speed. The good news is that external SSD is much cheaper than before and the price gap is much smaller.

Now, the big question is why you don't want to install macOS Catalina on your main hard drive. After all, if you're upgrading to macOS Catalina, you want your Mac to boot to it all the time, don't you? Not necessarily. There are several reasons why you might not want to disturb your current installation, whether it's Catalina or an older version of macOS. Here are some possible reasons.

● You might want to try macOS Catalina without having to uninstall and roll back to Mojave or High Sierra if you change your mind. Uninstalling and rolling back to an older version of macOS is time-consuming and a tedious process that is prone to errors, so you may not want the hassles that come with it.

● Your Mac (Mostly Mac Mini or iMac) is built upon on a HDD and it runs slowly. You are looking for a way to boost the performance without untouching the internal drive.

● Since there are bound to be bugs in early versions of any new OS, you might want to avoid the hassle of having it as your default OS. This way, you can update it as new versions are released, then install it as your main OS when you're happy with the stability of the software.

● You may want to have the SSD run macOS Catalina on more than one machine. Since your SSD is essentially an external drive that is portable, you may want to switch it between one Mac and the other. Instead of installing Catalina on both, you have the flexibility of simply connecting the SSD to one of the Macs when you want to boot from it.

● It's also possible that you want to run a different set of apps and, therefore, need more memory. If you use a larger-capacity SSD, this will allow you to load a ton of heavy apps like Photoshop and so on, which might not be possible with your current hard drive because it is already full of data.

How to Pick up the Right External SSD for Catalina

Mac computers are made different from PCs. It has its own hardware port and unique standards. So not all external SSDs are suitable for Macs. To maximize the performance of SSD, it should be USB 3.0 compatible, if you have enough budget, ThunderBolt port is more welcome as it has much faster reading and writing speed. Besides, the volume should be 128 GB or larger. Below is a list of best external SSDs for Mac:

Further reading: How to check hardware port on your Mac

• Adata SD600Q External SSD 240GB (USB 3.2, $39.16)
• SanDisk 500GB Extreme Portable External SSD (USB-C, $84.99)
• Samsung X5 Portable SSD 500GB (Thunderbolt 3, $199.99)
• LaCie Portable SSD STHK1000800 1TB (USB-C, $178.31 )
• G-Technology 0G06053 Portable External SSD 1TB (USB 3.0, $189.95)
• WD 500GB My Passport Go SSD (USB 3.0, $69.99)
• Seagate One Touch SSD External 1TB (USB 3.0, $144.99)

Notice: The SSD you are going to use or purchase should be compatible with your Mac.

Preparation before Getting Started

How To Install Catalina On Macbook Air

To instal Catalina on external SSD, there are quite a few things you should set up previously. The preparatory steps are very important because if you don't get them right, the time spent on the rest of the process will be completely wasted and you'll have to do it all over again. For that reason, make sure you follow the steps exactly as outlined. macOS Catalina is built on a different drive partition scheme, the APFS file system. This was introduced in Catalina for Mac but it's been in iOS for quite some time. In an effort to unify its desktop and mobile operating systems, Apple has now rolled out the new system to both branches of its core OS.

1. Download Catalina DMG File: For macOS installation, you have to create a bootable Catalina USB first. To do this, you need to get a copy of the Catalina dmg file.

Download link: http://www.mediafire.com/file/ /macOS_Catalina_DMG.rar

2. Format External SSD to APFS: APFS is the file system that holds macOS Catalina installation. The SSD is formatted to exFAT when it is shipped. You can format the external drive to APFS with Disk Utility app.

Connect the SSD to your Mac and launch Disk Utility. Select the external drive in the left-side panel and click Erase. In the pop-up, name your drive, select APFS, and GUID Partition Map.

3. Backup important data on your Mac: To avid data loss, it is highly recommended backing up your important data on internal SSD with Time Machine or Cloud Drive.

How to Create macOS Catalina Bootable USB Installer

After completing the above preparation, it is time to get into the part for creating a bootable Catalina USB installer. This can be done easily with the help of UUByte DMG Editor, a cross-platform program for making bootable USB drive from macOS dmg file.

Step 1: Please download UUByte DMG Editor on a PC or Mac and follow the on-screen tips to install this utility on your computer..

Step 2: Plug in an external USB flash drive and eject other USB devices at the same time. Now, open UUByte DMG Editor and click Burn tab.

Step 3: In Burn page, click Browse button to add macOS dmg file you downloaded to the program. After a few seconds, you can see the USB drive in secord field.

Step 4: Set a name for the new volume and click Burn button to start writing Catalina DMG file to USB drive. The file is around 8GB so it takes about 10 minutes to finish the task. Please be patient!

Creating macOS Big Sur install USB on Windows 10 is simple with the help of UUByte DMG Editor. It is one of the best tools for managing DMG file on a Windows PC.

How to Install Catalina on External SSD

You have done all the crucial steps in above part and the final step is how to install macOS Catalina on External SSD. This process is quite simple.

First, connect the SSD to your Mac. Then restart your Mac and hold the Option key until you see the Apple logo. In the Startup Disk, click the external drive name.

When the boot resumes, you should boot into macOS Catalina installation wizard. At this stage, you should pick up the external SSD to install Catalina.

How To Erase And Reinstall Macos Catalina

Another way to boot Catalina is from System Preferences. Here, go to the Startup Disk section, select your external SSD, and then hit Restart. Do not hold the Option or Alt key down if you're using this method.

Troubleshooting If Catalina Installation Failed

USB not bootable: If the USB drive is not showing up in Startup Manager, this means the USB drive is not recognized as a bootable device. Please download Catalina DMG file from another source and burn it again with UUByte DMG Editor. Sometimes, the partition table is missing in corrupted or damaged dmg file.

How To Reinstall Catalina On Macbook Pro

Can not boot into Catalina partition after installation: On latest T2 chip, Mac does not allow booting from external storage device by default. You have to enable 'Allow booting from external media' in Startup Security Utility, where you can launch it in macOS Recovery by pressing and holding Command + R immediately at startup.

Conclusion

Once you have macOS Big Sur installer USB ready, you can insert it into any Mac and run the program to install Apple's latest desktop operating system. Big Sur is officially coming in the fall and has a ton of updated features on nearly all fronts, including the OS interface, Safari, Siri, Messages for desktop, etc. But you should also know that since the currently available DMG is only a public beta tester version, it is bound to have bugs and other issues. If you're on the beta program, you can use the feedback app to let Apple know what the issue is. Unfortunately, that also means that there's nothing you can do about it if you're not on the beta program.