Use an external storage device as a Mac startup disk

1. Connect your storage device to your Mac.
2. Check the format of your storage device.
3. Install macOS on your storage device.
4. Allow booting from external media.
5. Select your storage device as the startup disk.
6. Keep macOS up to date on the storage device.

How to boot a Mac from a USB:

1. Download the macOS installer from the App Store.
2. Install the macOS installer onto a clean and Mac OS Extended or APFS (for Apple Silicon Mac) formatted USB.
3. Boot your Mac from this bootable USB.

On your Mac, choose Apple menu > System Settings, click General in the sidebar, then click Startup Disk on the right. (You may need to scroll down.) Click the icon of the disk you want to use, then click Restart.

How do I boot my Mac from a USB installer : Boot Mac from USB Media

Press and hold the Option (Alt) key on the keyboard when the computer starts. Select the USB drive as a startup disk when the option appears. The system will start the boot process off the USB drive. Install the operating system from the macOS utilities.

Can I boot from an external hard drive

If you want to set your computer to boot from an external hard drive, you'll need to access the BIOS, which is a control panel that you open by pressing repeatedly a key (usually a function key such as F12) as your computer starts up.

Why won’t my Mac boot from an external drive : If your Mac is equipped with Apple's T2 Security Chip, you may need to enable booting from external media first. To do this, Boot your Mac into Recovery Mode by holding Command+R while starting up. Go to Utilities > Startup Security Utility, and enable "Allow booting from external media."

Turn on your Mac and continue to press and hold the power button as your Mac starts up. Release the power button when you see the startup options screen, which shows your startup disks and a gear icon labeled Options.

First and foremost, your macOS version may not be compatible with your Mac. And if you start your Mac from a USB device with a different macOS version than your Mac supports, you may face issues. It could also be that the USB device contains damaged or incompatible data or software, stopping your Mac from starting.

How to boot from an external hard drive

Setting up Your External Hard Drive

1. 1 Figure out your computer's BIOS key on Windows.
2. 2 Attach the external hard drive to your computer.
3. 3 Format the hard drive if necessary.
4. 4 Make sure you have an item from which to boot.
5. 5 Place the boot file on the external hard drive.
6. 6 Make the external hard drive bootable.

You can use a USB flash drive or other secondary volume as a startup disk from which to install the Mac operating system.Disable USB Legacy Support

The computer may boot correctly with the external hard drive connected if USB Legacy Support is disabled. USB Legacy Support enables the computer to use USB peripherals without running operating system drivers and can cause the system to hang on boot when an external hard drive is connected.

A bootable external hard drive also does great help when a computer's dead or crashed. Besides, with a bootable external USB drive, you can use your own operating system wherever you go and whenever you like.

How do I force boot from an external hard drive : Select your external hard drive.

Find your external hard drive's name or classification (e.g., External Hard Drive) in the "Boot Order" list, then press the "Down" arrow key until the external hard drive is selected. In some cases, you'll only be able to select USB devices (or similar) in this menu.

How to boot M1 Mac with recovery key : Step 1: Shut down or restart your Mac using the b>Apple icon in the Menu bar. Step 2: Hold down the Command + R keys on your Intel Mac keyboard. Step 3: Turn on your Intel Mac using the Power button or wait for it to restart. Step 4: Keep holding the keys until you see the Apple logo or a spinning globe.

Why is USB not booting

When Windows can't boot from USB, you need to make sure your bootable USB drive is formatted in the FAT32 file system if your computer supports UEFI and you are attempting to install Windows in UEFI mode. That is, you cannot use a USB drive with the NTFS file system to boot and install Windows in UEFI mode.

Open System Information and disconnect the USB device from your computer. Wait a few minutes, and click File > Refresh Information. Reconnect the USB device. You should see a device disappear from System Information when you remove the USB device, and it should appear again when you reconnect it.To boot from your USB drive, you will need to insert the drive into your computer and then press the power button. Once the computer has turned on, press the 'F11' or 'Delete' keys repeatedly until you reach the boot menu. From here, select 'Boot from USB' and choose your drive from the available options.

How to run OS from external hard drive : Setting up Your External Hard Drive

1. 1 Figure out your computer's BIOS key on Windows.
2. 2 Attach the external hard drive to your computer.
3. 3 Format the hard drive if necessary.
4. 4 Make sure you have an item from which to boot.
5. 5 Place the boot file on the external hard drive.
6. 6 Make the external hard drive bootable.