An external drive that you can use as an installer for macOS Catalina is a handy thing to have. If you have multple Macs to upgrade, it’s a lot more efficient to plug in the USB installer drive and run the installer than to log into the App Store, download the 8.09GB OS installer, and then run it.

Download: macOS Big Sur, macOS Catalina, macOS Mojave or macOS High Sierra These will be downloaded to your Applications folder as an app named Install macOS version name. If the installer opens after downloading, quit it without continuing installation. In this topic, we share the download links of all MacOS X versions from 10.4 to 10.15: Catalina, Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion, Lion, Snow Leopard, Leopard and Tiger - all original and downloaded from Apple Store. All the following shared MacOS Installer.app files had been originally downloaded from Apple Store. Both related.ISO and.DMG images.

MacOS Catalina Bootable Installer (macOS Catalina DMG) Now that you have the “macOS Catalina.app” installer, you can upgrade multiple Macs to the latest version using the same file. However, if you are looking to perform a fresh installation, you need to create a bootable installer for Catalina. Nov 12, 2020 Make a bootable installer of macOS Big Sur so you can have a portable copy to install on multiple devices. IPad Air deal at Amazon: Grab the 256GB model at $69 off. What’s needed for a clean install on a Mac A backup of the disk before it’s erased. Two options are to use Duplicate (a free utility which can copy and paste an entire bootable volume), or Mac Backup Guru (a paid, fully featured backup utility with unique incremental backups capability) for that. Here is a detailed guide for the process. A Mac operating system installer. MacOS Big Sur can.

In this article I’ll go over the different ways you can create a bootable macOS Catalina installation drive. But before I give instructions on how to create the drive, I’ll go over the items you’ll need and how to get them.

Get an external drive and maybe an adapter

The macOS Catalina installer software is over 8GB, so you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.

If you have a 2015 or newer MacBook or a 2016 or newer MacBook Pro, you may need Apple’s $19 USB to USB-C adapter. This will allow you to connect a storage device that uses a USB type-A connector. If you don’t have an external drive and you have a USB-C Mac laptop, you could buy the SanDisk Ultra USB Type-C Flash Drive, which has a USB-C connector. You can get model number SDCZ450-016G-G46.

When creating the boot drive, the storage device is reformatted, so there’s no need to format the drive beforehand.

Get the macOS Catalina installer software

The macOS Catalina installer is available in the App Store. If you launch the App Store app, do a search for “Catalina.” Or, if you click this Catalina App Store link, it will take you to the Catalina App Store webpage, then click on the “View in the Mac App Store” button.

You can read the information to learn more about Catalina. When you’re ready to download the software, click the Download button. (If you’ve already downloaded the installer, the button will say Install instead of Get.)

Once the download is complete, the installer will launch automatically. But don’t continue with the installation. Instead, press Command-Q on your keyboard to quit the installer.

The Catalina installer app will be in your Applications folder, so you can go there and launch it later to upgrade your Mac to the new operating system.

Make a bootable installer drive: The quick way

I used a free app called Install Disk Creator to make the installation drive. Download Install Disk Creator by clicking on the link. When the download is done, you can move it over to your Applications folder. Then follow these steps to create your bootable macOS Catalina drive.

1. Connect your drive to your Mac.

2. Launch Install Disk Creator.

3. In the main window, you’ll see a pop-up menu under Select the volume to become the installer. Click on the menu and select your drive.

4. Under the pop-up menu, you’ll see Select the OS X installer. (macOS used to be called OS X.) If you have only the Catalina installer on your Mac, Install Disk Creator will automatically select it. If you have other macOS installers, you need to click on Select the OS X installer and select the Catalina installer.

5. When you’re ready, click Create installer. Your Mac may tell you that Install Disk Creator wants to make changes, and you need to enter your user name and password. After you do this, the app will take a few minutes to create the boot drive. A progress bar. appears at the bottom of the Install Disk Create window.

If you try to start the process and you get a failure message saying that the drive couldn’t be unmounted, try reformatting the drive first as ExFAT using Disk Utility. Then start the process over again.

When the app is done, the installer is ready to use.

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

What you need to create a bootable installer

Macos Catalina Install Boot Loop

• A USB flash drive or other secondary volume, formatted as Mac OS Extended, with at least 12 GB of available storage
• A downloaded installer for macOS Big Sur, Catalina, Mojave, High Sierra or El Capitan

Download macOS

• Download: macOS Big Sur, macOS Catalina, macOS Mojave or macOS High Sierra
  These will be downloaded to your Applications folder as an app named Install macOS [version name]. If the installer opens after downloading, quit it without continuing installation. To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.
• Download: OS X El Capitan
  This will be downloaded as a disk image named InstallMacOSX.dmg. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It will install an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

1. Connect the USB flash drive or other volume that you're using for the bootable installer.
2. Open Terminal, which is in the Utilities folder of your Applications folder.
3. Type or paste one of the following commands in Terminal. These assume that the installer is in your Applications folder and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.

Big Sur:*

Catalina:*

Macos Catalina Bootable Installer Mojave

Mojave:*

High Sierra:*

El Capitan:

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument and installer path, similar to the way this is done in the command for El Capitan.

After typing the command:

1. Press Return to enter the command.
2. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
3. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the volume is erased.
4. After the volume has been erased, you may see an alert stating that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
5. When Terminal says that it's been completed, the volume will have the same name as the installer you downloaded, such as Install macOS Big Sur. You can now quit Terminal and eject the volume.
   

Use the bootable installer

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
2. Turn on your Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes and a gear icon labelled Options.
3. Select the volume containing the bootable installer, then click Continue.
4. When the macOS installer opens, follow the onscreen instructions.

Intel processor

1. Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing.
2. Press and hold the Option (Alt) ⌥ key immediately after turning on or restarting your Mac.
3. Release the Option key when you see a dark screen showing your bootable volumes.
4. Select the volume containing the bootable installer. Then click the up arrow or press Return.
   If you can't start up from the bootable installer, make sure the External Boot setting in Startup Security Utility is set to allow booting from external media.
5. Choose your language, if prompted.
6. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Learn more

For more information about the createinstallmedia command and the arguments that you can use with it, make sure the macOS installer is in your Applications folder, then enter the appropriate path in Terminal:

• Big Sur: /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia
• Catalina: /Applications/Install macOS Catalina.app/Contents/Resources/createinstallmedia
• Mojave: /Applications/Install macOS Mojave.app/Contents/Resources/createinstallmedia
• High Sierra: /Applications/Install macOS High Sierra.app/Contents/Resources/createinstallmedia
• El Capitan: /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia

A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.