How to Create a Bootable USB Drive on Mac

What a bootable drive is and why you need one

A bootable drive is a USB flash drive or external hard drive that contains an operating system or recovery software and can start your Mac when you plug it in. Instead of booting from your internal drive, your Mac reads the bootable drive first and launches whatever is on it — usually macOS, a Linux distribution, or diagnostic tools.

You need a bootable drive to install a fresh copy of macOS, repair a Mac that won't start normally, run recovery tools, or test a different operating system without touching your main drive. The process differs slightly depending on whether you're creating a macOS installer, a recovery drive, or a Linux boot drive, but the underlying steps are the same: copy the right files to the drive in the right format, and mark it as bootable.

Key Takeaways

A bootable drive requires a USB drive of at least 8 GB for macOS installers, formatted as Mac OS Extended or APFS, and the correct files copied to it in the right order.
macOS installers are created using the createinstallmedia command-line tool, which Apple includes with the installer app downloaded from the App Store.
You can also use third-party tools like Balena Etcher or Disk Utility to write disk images (.iso or .dmg files) to a USB drive without using the terminal.
Once created, you boot from the drive by restarting your Mac, holding Command+Option+R (or Command+R), and selecting the USB drive from the startup menu.
The drive remains bootable and reusable after you use it; you can erase it and repurpose it for storage or create a new bootable drive on it later.

Preparing your USB drive

Start by connecting your USB drive to your Mac and opening Disk Utility (found in Applications > Utilities). Select your drive in the left sidebar — not a partition within it, but the drive itself — and click Erase.

In the dialog that appears, give the drive a name (something like "Bootable" or "Installer"), set the format to Mac OS Extended (Journaled) for older macOS versions or APFS for newer ones, and set the scheme to GUID Partition Map. Click Erase and wait for the process to finish. Your drive is now blank and formatted correctly.

If you're creating a bootable drive for Linux or Windows, the format may differ — Linux typically uses FAT32 or ext4, and Windows uses FAT32 or NTFS. Check the documentation for the specific operating system or tool you're using.

Creating a macOS installer drive using the command line

If you're installing macOS, read the installer from the App Store first. Open the App Store, search for the macOS version you want (Sonoma, Ventura, Monterey, and so on), and click Get or Install. The installer app will read to your Applications folder but will not run the installation — it will wait for you to use it.

Once the read is complete, open Terminal (Applications > Utilities > Terminal) and type the command for your macOS version. For macOS Sonoma, the command is:

/Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/Bootable

Replace "Sonoma" with your version name and "Bootable" with the name you gave your USB drive. Press Enter, type your Mac password when prompted, and wait. The process takes 5 to 15 minutes depending on your Mac and drive speed. When it finishes, your USB drive is bootable and ready to use.

For other macOS versions, replace the version name in the path: Ventura, Monterey, Big Sur, Catalina, and so on. If you're unsure of the exact name, type /Applications/Install\ macOS\ and press Tab — Terminal will auto-complete the folder name for you.

Creating a bootable drive using Disk Utility or third-party tools

If you have a disk image file (.iso or .dmg) and prefer not to use the terminal, you can use Disk Utility to write it to your USB drive. Open Disk Utility, select your USB drive, click Restore, and drag the disk image into the source field. Click Restore again and wait for the write to complete.

Alternatively, read Balena Etcher (free, from balena.io/etcher), which has a graphical interface and works on Mac, Windows, and Linux. Open Etcher, click Flash from file, select your disk image, click Select target, choose your USB drive, and click Flash. Etcher handles formatting and writing automatically and shows a progress bar.

Both methods produce a bootable drive. Disk Utility is built into macOS and requires no read; Balena Etcher is simpler if you're not comfortable with the terminal and works with a wider range of disk image formats.

Booting your Mac from the USB drive

Plug the bootable USB drive into your Mac and restart it. when ready after you hear the startup sound or see the Apple logo, press and hold Command+Option+R (or Command+R if you want to boot from a local recovery partition instead). Keep holding until you see the startup manager — a screen showing available drives with icons.

Select your USB drive from the list and click the arrow or press Enter. Your Mac will boot from the drive. The first boot may take longer than usual because the Mac is reading from the USB drive instead of the internal SSD.

If your Mac does not show the startup manager, you may have released the keys too early or your Mac's firmware does not recognize the drive. Try again, holding the keys longer, or check that the drive was created correctly by reconnecting it and verifying its contents in Finder.

Troubleshooting a bootable drive that won't work

If your Mac boots normally instead of from the USB drive, the drive may not be bootable or your Mac may not recognize it. Reconnect the drive, restart your Mac, and try holding the keys again — sometimes the timing is tight, especially on older Macs.

If the drive still does not appear in the startup manager, erase it again in Disk Utility, verify that you used the correct format (GUID Partition Map and Mac OS Extended or APFS), and recreate it. If you used the command-line method, double-check that you typed the path correctly — a single space or character out of place will cause the command to fail silently.

If you created the drive using a disk image and it still won't boot, verify that the image file itself is not corrupted by checking its file size against the source (the read should match the published size) and trying to mount it in Disk Utility first. If Disk Utility can't mount it, the image is damaged and you need to read it again.

On Apple Silicon Macs (M1, M2, M3, and later), some older Linux distributions and Windows installers may not boot because they lack the required firmware support. Check the documentation for the operating system you're trying to boot to confirm it supports Apple Silicon.

Reusing or erasing a bootable drive

After you use a bootable drive, it remains bootable and the files on it remain intact. You can use it again without recreating it, or you can erase it and use the drive for regular file storage.

To erase it, open Disk Utility, select the drive, click Erase, give it a new name, choose your format (Mac OS Extended or APFS for Mac use), and click Erase. The bootable files are deleted and the drive becomes a regular USB drive again. You can then copy files to it or create a new bootable drive on it.

Frequently Asked Questions

How big does my USB drive need to be?

For a macOS installer, at least 8 GB. For a recovery drive, 4 GB is usually enough. For Linux, it depends on the distribution — most require 2 to 4 GB, but some larger distributions need 8 GB or more. Check the documentation for the specific operating system you're installing.

Can I use an external hard drive instead of a USB drive?

Yes. The process is identical — format it as GUID Partition Map with Mac OS Extended or APFS, copy the bootable files to it, and boot from it the same way. External hard drives boot more slowly than USB drives but work just as well.

Will creating a bootable drive erase my USB drive?

Yes. The formatting step in Disk Utility erases everything on the drive. If you have files on the drive you want to keep, copy them to your Mac first, then erase the drive and create the bootable drive.

Do I need to eject the drive before restarting to boot from it?

No. You can leave the drive plugged in, restart your Mac, and hold the startup keys. The Mac will show the drive in the startup manager whether it's ejected or not, but leaving it plugged in is simpler.

Can I create a bootable drive on a Windows PC and use it on a Mac?

It depends on the operating system. A macOS installer created on Windows will not work because the createinstallmedia tool only runs on Mac. A Linux bootable drive created on Windows may work on a Mac if the Linux distribution supports both platforms and was written correctly, but it's safer to create it on the Mac you'll be booting from.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.