Creating a bootable USB drive with macOS

A bootable USB drive lets you install macOS from a USB drive instead of downloading the installer again during setup. It can help when macOS will not install normally, or when you need to install the same macOS version on more than one compatible Mac.

Apple provides a built-in tool called createinstallmedia for this process. You do not need special third-party software.

This guide explains how to download the full macOS installer, prepare the USB drive, create the installer, and start a Mac from it.

What You Need

You need a Mac that can download the macOS installer and a USB flash drive.

A 32GB USB drive is a good choice for modern macOS installers. Apple says 16GB is enough for many older versions. A USB drive with USB-C can also be used if your Mac has USB-C ports.

You also need the full macOS installer app. A small update file is not enough.

When Should You Create a Bootable USB?

You may not need one for a normal macOS installation.

A bootable installer is useful if macOS will not start correctly, Recovery is not working, or you want to install macOS on several compatible Macs.

It can also save time when you already have the full installer and do not want each Mac to download it again.

A bootable installer does not give you a complete copy of macOS that runs from the USB drive. It is an installer. You use it to install macOS on a Mac.

Step 1: Download the Full macOS Installer

First, download the macOS version you want to install.

Apple provides full macOS installers through the App Store, its support pages, and Terminal.

When the download finishes, the installer should normally appear in the Applications folder.

For example, you may see:

Install macOS Tahoe.app

Or:

Install macOS Sequoia.app

Do not start the installation. If the installer opens automatically, close it.

Keep the installer in the Applications folder because the Terminal command needs to find it there.

You can also learn about the different macOS releases in our macOS versions in order guide.

Check the Installer Before You Start

Open the Applications folder and look for the macOS installer.

The name must match the version you want to put on the USB drive.

For example:

Install macOS Sonoma.app

The name matters because the Terminal command uses the exact installer name.

If the installer is missing, download the full installer again before continuing.

Download a Full Installer With Terminal

You can use Terminal to see which full macOS installers are available for your Mac.

softwareupdate --list-full-installers

Your Mac will show the macOS versions that are available.

To download a specific version, use:

softwareupdate --fetch-full-installer --full-installer-version 26.3

Replace 26.3 with the version you need. The available versions can change depending on the Mac you are using.

Step 2: Connect the USB Drive

Connect your USB drive directly to the Mac.

If your Mac only has USB-C ports, you can use a USB-C flash drive or a suitable adapter.

Back up anything important from the USB drive first.

The creation process will erase the drive.

Step 3: Give the USB Drive a Simple Name

Apple’s example commands use the name MyVolume.

You can rename your USB drive to MyVolume before running the command.

Open Finder and find the USB drive under Locations. Right-click it and select Rename.

Type:

MyVolume

This makes the Terminal command easier to copy.

Step 4: Open Terminal

Open:

Applications > Utilities > Terminal

You will use one command to turn the USB drive into a bootable macOS installer.

Step 5: Run the Correct Command

Apple includes the createinstallmedia tool inside the full macOS installer.

Copy the command that matches the installer you downloaded.

macOS 27 Golden Gate

sudo /Applications/Install\ macOS\ 27\ Golden\ Gate.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Tahoe

sudo /Applications/Install\ macOS\ Tahoe.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Sequoia

sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Sonoma

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

macOS Ventura

sudo /Applications/Install\ macOS\ Ventura.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Monterey

sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Big Sur

sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Catalina

sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS Mojave

sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

macOS High Sierra

sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

Older macOS versions may use a slightly different command. Check Apple’s instructions for the exact version before using an older installer.

Step 6: Enter Your Mac Password

After you run the command, Terminal may ask for your Mac password.

Type your password and press Return.

Nothing may appear on the screen while you type. This is normal.

The command will then ask for permission to erase the USB drive.

Type:

Y

Then press Return.

The USB drive will be erased and the installer files will be copied to it. Do not disconnect the USB drive during this process.

What Happens Next?

Terminal will show progress as it creates the installer.

The process can take some time.

When it finishes, you should see a message similar to:

Install media now available at "/Volumes/Install macOS ..."

The USB drive may also change its name to match the macOS installer.

Step 7: Eject the USB Drive

After the process finishes, eject the USB drive before removing it.

In Finder, right-click the USB drive and select Eject.

You can now use the USB installer with a compatible Mac.

How to Start an Apple Silicon Mac From the USB

Macs with Apple silicon have a different startup process from older Intel Macs.

Connect the bootable USB drive directly to the Mac.

Shut down the Mac completely.

Press and hold the power button.

Keep holding it until you see the startup options.

The USB installer should appear as a startup option.

Select it and choose Continue.

The Mac will start from the installer and show the available macOS installation tools.

The exact options can vary depending on the Mac and macOS version.

How to Start an Intel Mac From the USB

Connect the USB installer to the Mac.

Shut down the Mac.

Turn it on and immediately press and hold the Option or Alt key.

Keep holding the key until you see the available startup drives.

Select the USB installer and press Return.

The Mac should start from the USB installer.

What About Intel Macs With the T2 Security Chip?

Some Intel Macs have Apple’s T2 security chip.

These Macs have additional startup security settings. In some cases, an external USB installer may not appear as a startup option because of these settings.

If the USB installer is not showing on a compatible T2 Mac, check the Mac’s startup security settings.

Apple Silicon Macs Work Differently

Apple silicon Macs have a different startup and security system from Intel Macs.

This means instructions written for older Intel Macs may not apply to newer Macs.

You should not assume that an Apple silicon Mac needs the same security changes as an Intel Mac.

For a normal Apple-supported macOS installer, start with Apple’s standard startup process. Additional security changes may be relevant when using older macOS versions or other types of external systems.

Check Mac Compatibility Before Installing

Creating the USB installer does not mean that every Mac can install that version of macOS.

Each macOS release supports a specific group of Mac models.

Check the compatibility list for the macOS version you want to install.

This is especially important when using an older Mac.

A USB installer can be created successfully and still fail to install if the Mac does not support that macOS version.

If you are unsure which version your Mac supports, our macOS versions guide is a useful starting point.

Why Does the USB Installer Fail?

Most problems come from a small number of causes.

The wrong installer is often the first thing to check. Make sure the full installer is in the Applications folder.

The command must also match the exact name of the installer.

For example, a command for Sonoma will not work if you downloaded Ventura.

The USB drive name also matters. If you use MyVolume in the command, the USB drive should have that name.

The USB drive can also cause problems. If the current drive keeps failing, try another USB drive.

Terminal Says “Command Not Found”

This usually means Terminal cannot find the file or command you entered.

Check the following:

• Make sure the installer is in the Applications folder.
• Check the installer name.
• Make sure the spaces in the command are written correctly.
• Make sure you are using the command for the correct macOS version.

For example, this part:

Install\ macOS\ Sonoma.app

must match the actual installer name.

Terminal Says the Installer Is Not Valid

You may see an error saying that the installer application is not valid.

This can happen if the downloaded installer is incomplete or damaged.

Download the full installer again. Also check that you downloaded the full macOS installer app rather than a smaller installation package.

The USB Drive Cannot Be Erased

If createinstallmedia cannot erase the USB drive, open Disk Utility.

Select the physical USB drive and erase it.

For Apple’s manual preparation steps, Mac OS Extended (Journaled) with a GUID Partition Map is commonly used.

After erasing the drive, run the correct createinstallmedia command again.

The USB Does Not Appear at Startup

First, make sure the USB installer was created successfully.

Then try another USB port.

If you are using a hub or adapter, connect the USB drive directly if possible.

Also check that the Mac supports the macOS version on the USB drive.

For an Intel Mac with a T2 security chip, check the startup security settings if the installer still does not appear.

For Apple silicon Macs, use the power button startup process rather than the old Option key method.

The Creation Process Looks Stuck

Do not immediately unplug the USB drive.

The process can take time, especially with a slower USB drive.

If Terminal stops for a very long time and shows no progress, check the USB connection.

You can also try creating the installer again with another USB drive.

Should You Use APFS or Mac OS Extended?

You normally do not need to choose the final format yourself.

The createinstallmedia tool prepares the USB drive as part of the process.

If you need to manually erase the USB drive first, follow Apple’s instructions for the macOS version you are preparing.

Do not format the USB randomly just because another guide recommends a different format.

The bootable installer process is different from installing a complete copy of macOS on an external SSD.

Can You Create a macOS USB Installer on Windows?

Apple’s official method requires macOS because it uses the full macOS installer and Apple’s createinstallmedia tool.

If you only have a Windows PC, the process is different and may require third-party methods.

For the most reliable Apple-supported process, create the installer from a Mac.

Can You Use One USB Installer on Several Macs?

Yes, if the Macs are compatible with that macOS version.

This is one of the main reasons Apple provides bootable installers.

For example, if you manage several compatible Macs, you can use the same USB installer instead of downloading the installer separately on every Mac.

The Macs still need to support the macOS version on the USB drive.

Can You Use a 16GB USB Drive?

It depends on the macOS version.

Apple says 16GB is enough for most earlier macOS versions.

For newer versions, a 32GB USB drive is a safer choice.

A larger USB drive does not make macOS itself run faster. The speed of the USB drive can affect how quickly files are copied and how responsive the installer feels.

Can You Use a USB-C Drive?

Yes.

A USB-C flash drive can be used if it is compatible with your Mac.

USB 3 or faster storage can also reduce the time needed to copy the installer.

If you use an adapter, make sure the connection is stable.

Can You Reuse the USB Drive Later?

Yes.

After you finish installing macOS, you can erase the USB drive and use it for normal file storage.

Remember that creating the installer erases the existing contents of the drive.

Do not use the USB drive for important files unless you have another copy of them.

Bootable Installer vs External macOS Drive

These two things are often confused.

A bootable installer contains the tools needed to install macOS. It is mainly used to start the installation process.

An external macOS drive contains a complete macOS system installed on the external drive.

They are not the same thing.

If your goal is to install macOS on an internal drive, the Apple createinstallmedia method is the correct approach.

If your goal is to run macOS directly from an external SSD, you need a different setup.

A Simple Troubleshooting Method

If your bootable USB does not work, do not change several things at once.

Start with the installer. Make sure it is the full installer and that it is in the Applications folder.

Next, check the command. Make sure the macOS version in the command matches the installer you downloaded.

Then check the USB drive. Make sure the correct drive is connected and that its name matches the command.

Finally, check the Mac. Make sure the Mac supports that macOS version and use the correct startup method for Apple silicon or Intel.

This simple process can help you find the problem without repeating the entire setup unnecessarily.

Quick Reference

Final Checklist

After the installer is created:

Final Thoughts

Creating a bootable USB drive with macOS is easier than it first looks.

The most important part is using the full macOS installer and the correct createinstallmedia command.

The USB drive will be erased, so back up its files first.

If the installer does not work, check the installer name, USB drive, command, Mac compatibility, and startup method before trying more complicated fixes.

Apple’s built-in method is usually the best place to start because it does not require extra installer software.