Dual Boot Mac: Install macOS Monterey/Big Sur/Catalina & Mojave, Two macOS on Different Partition

Installed MacOS on Dual Boot Mac
Installed MacOS on Dual Boot Mac

How to Create New Partition for macOS Monterey, Mojave on macOS Catalina after that install and Run Dual MacOS? Installing and using two different macOS on Mac that isn’t simple like Windows. Many of us are familiar with the older version of macOS and don’t wont to update to the latest version, but still want to use the newest features of macOS, isn’t this an utterly confusing situation? If you are stuck in this situation, then this article is for you. From creating a new partition to switching between macOS, we have covered every single step that will help you to dual boot Mac and install two macOS on MacBook/Mac.

The process to create a dual boot Mac and install two macOS on the same Mac is divided into seven parts. These seven parts will help you create two macOS on the same Mac, without any misinterpretation. Follow along with the tutorial. Let’s Get the Perfect Solution for the Problem of “This copy of the “Install macOS” application is too old to be opened on this version of macOS.” and Don’t leave New Upgrade MacOS.

  1. Create a new partition to install earlier macOS.
  2. Download macOS from app store.
  3. Create a macOS bootable drive.
  4. Install macOS on another partition created on your Mac.
  5. Switch between two different macOS.
  6. Setup macOS.
  7. Now you can use between macOS Mojave and macOS Catalina on your Mac.

Here is the complete video tutorial,

Part 1: Create a New Partition on a Mac

Since you want to use two different macOS on the same Mac, it is necessary to create a new partition. Creating a new partition on Mac won’t affect the existing partitions and data stored on it. Here’s how to do it,

Step #1: Launch “Spotlight search” (command+space) and open “Disk Utility”.
Step #2: Select the Hard drive from the left panel.
Step #3: Click “Partition”.
Step #4: Again click “Partition”.
Step #5: Name the partition and set the Disk Size of the new partition.
Step #6: Click on “Apply”.
Step #7: A pop-up will revise to you what will happen when you create a new partition on Mac.
Note: No partitions will be erased on your Mac.
Step #8: Hit “Partition”.

Create a New Partition on Mac
Create a New Partition on Mac

Step #9: When the new partition is created, the system stops responding until the process gets completed, select “Continue”.
Step #10: Wait for a while, when a new partition is created on your macOS, click “Done”.

Part 2: Download MacOS on Your Mac [Running MacOS Catalina Mac]

Apple won’t allow you to download the macOS Mojave directly from the Mac App Store once you update to macOS Catalina. Therefore, we have given a direct link to download the macOS Mojave. Surely, this link will take you to the Mac App Store, but when you search for macOS Mojave in the Mac App Store, it won’t show you.

Step #1: Click here to download macOS Mojave on Mac.
Step #2: The link will redirect you to Mac App Store, from there download the macOS Mojave.
Step #3: Go to the “Applications”, using Spotlight search (command+space).

Download MacOS Mojave from MacOS catalina
Download MacOS Mojave from MacOS catalina

Step #4: Make sure the Install macOS Mojave file is there in the Applications folder.

Part 3: Time to Create Bootable Drive [macOS Mojave Bootable Drive]

Next step is to create Bootable Drive to install the macOS Mojave on a separate partition. Make sure to back up the USB drive, as you will need to Erase it later.

Step #1: Plug the USB Drive on your Mac.

Note: You should use a minimum 16GB USB Drive for faster and better operations. Also, take a backup of the drive that you are using.

Make a Bootable Drive on Mac
Make a Bootable Drive on Mac

Step #2: Open the “Disk Utility” and “Erase” the drive.
Step #3: Launch “Terminal” from the Spotlight search (command+space).
Step #4: Type the following command,

sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia –volume /Volumes/[Your USB Drive Name]

Note: Replace the USB Drive name with [Your USB Drive Name].

Step #5: Type “Y” and hit return.

Part 4: Install New macOS on Another Partition

Finally, you are ready to install macOS Monterey/Mojave on another partition of your Mac. Here’s how to do it.

Step #1: Turn off Mac, click on the “Apple” menu and select “Shut Down”.
Step #2: Know your Mac is Intel or M1.

  1. For M1 Mac: Press and Hold Power button [Touch ID Button], until your Mac show startup volume on screen. Now, your Mac will see bootable macOS Drive, Click on start the installation.
  2. For Intel Mac: Turn on Mac and after hear the startup sound immediately hold the “Option” key until the Mac screen show the Startup Disks.

Step #3: Click on “Install macOS Mojave” or “Install macOS Monterey” Bootable USB Drive. Wait for Few seconds.

Install MacOS from Bootable Drive
Install MacOS from Bootable Drive

Step #4: On the macOS Utilities tab, choose “Install macOS”.
Step #5: Click “Continue”, to begin setting up the installation of macOS.
Step #6: “Agree” to the Terms and Conditions.
Step #7: Now, you have to select the newly created partition that we have created in Part 1, to install macOS on another new partition.

Attention Note: On selecting the Primary Drive, you can downgrade So don’t interrupt primary drive.

Step #8: Click “Continue”. Follow the on screen instructions.

Part 5: Set Up MacOS

All Done! You have installed macOS on another partition of your Mac. Now, follow the on-screen instructions and set up macOS like Language, Region, Apple ID, etc. the information will be required. Besides, one option will ask you to Transfer Information to This Mac, select appropriate option.

Part 6: Switch Between MacOS Monterey/Mojave & MacOS Catalina

You cannot switch macOS without turning off. To switch between macOS, shut down the Mac and turn on by pressing and holding the Option [Alt] key. During startup drive, select between macOS Monterey/Mojave and macOS Catalina.

For M1 Mac: Press and Hold Power button [Touch ID Button] until you see startup volumes, after Restart or Start your Mac.

For Intel Mac: Press and Hold Shift Key after Restart or Turn on your Mac.

Installed MacOS on Dual Boot Mac
Installed MacOS on Dual Boot Mac

Now you can use Different software on Both the MacOS if Latest Version of MacOS isn’t compatible with [This copy of the “Install macOS” application is too old to be opened on this version of macOS.]. Some Users are getting message on install or open app but they don’t leave new MacOS that might be Beta version or Public MacOS.

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