How to Create a Bootable macOS USB Installer

Introduction

Creating a bootable macOS USB installer is essential for clean installations, troubleshooting, or setting up multiple Mac computers. This comprehensive guide covers the complete process using Apple’s official createinstallmedia command-line tool, with support for all macOS versions from Mavericks to the latest Sequoia.

Prerequisites

Before you begin, ensure you have:

A USB flash drive with at least 16GB of storage
The macOS installer app downloaded to your Applications folder
Administrator privileges on your Mac
Terminal app access

Downloading macOS Installers

You can obtain macOS installers through two methods:

Option 1: Mac App Store

Download the macOS installer directly from the Mac App Store. The installer will automatically appear in your Applications folder. If it opens automatically after downloading, quit the installer before proceeding.

Option 2: Terminal Download

For specific versions, you can use the Terminal command:

softwareupdate --fetch-full-installer --full-installer-version 15.5

Preparing Your USB Drive

Insert your USB flash drive and ensure it’s properly mounted. You can use Disk Utility to format it as Mac OS Extended (Journaled) or APFS before proceeding, though the createinstallmedia command will erase and format the drive automatically.

Complete Command Reference

The basic syntax for the createinstallmedia command is:

sudo /Applications/[InstallmacOSApp].app/Contents/Resources/createinstallmedia --volume /Volumes/[VolumeName]

Latest macOS Versions (2024-2025)

macOS Sequoia (15)

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

macOS Sonoma (14)

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

macOS Ventura (13)

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

Recent macOS Versions

macOS Monterey (12)

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

macOS Big Sur (11)

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

macOS Catalina (10.15)

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

macOS Mojave (10.14)

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

Legacy macOS Versions

For older versions, you need to include the --applicationpath parameter:

macOS High Sierra (10.13)

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

OS X El Capitan (10.11)

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

Advanced Options

Non-Interactive Mode

Add the --nointeraction flag to skip confirmation prompts:

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

Audio Notification

Add an audio notification when the process completes:

sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/untitled --nointeraction && say "Installation macOS Monterey Done"

Step-by-Step Process

Open Terminal: Launch Terminal from Applications > Utilities
Enter the command: Type the appropriate createinstallmedia command for your macOS version
Enter your password: Provide your administrator password when prompted
Confirm the action: Type ‘Y’ when asked to erase the volume (unless using –nointeraction)
Wait for completion: The process typically takes 20-30 minutes

Expected Output

A successful installation will show progress similar to this:

$ sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/untitled --nointeraction
Password:
Erasing disk: 0%... 10%... 20%... 30%... 100%
Making disk bootable...
Copying to disk: 0%... 10%... 20%... 30%... 40%... 50%... 60%... 70%... 80%... 90%... 100%
Install media now available at "/Volumes/Install macOS Monterey"

Troubleshooting Common Issues

Invalid Volume Error

Ensure your USB drive is properly mounted and the volume name is correct. Check available volumes using:

ls /Volumes/

Insufficient Space

Use a USB drive with at least 16GB of free space. The installer requires substantial storage.

Permission Denied

Make sure you’re using sudo and have administrator privileges on your Mac.

Expired Certificates

For older installers with expired certificates, download a fresh copy from the Mac App Store or use alternative download methods.

Best Practices

Use high-quality USB drives: Choose reputable brands for better reliability
Verify the installer: Ensure the macOS installer is complete and not corrupted
Keep backups: Create multiple bootable installers for different macOS versions
Test the installer: Verify the bootable drive works before you need it
Label your drives: Clearly mark each installer with the macOS version

Using Your Bootable Installer

To boot from your USB installer:

Connect the USB drive to your Mac
Restart your Mac and hold the Option (⌥) key
Select the USB installer from the startup options
Follow the on-screen instructions to install macOS

Alternative Resources

For additional macOS installer resources, consider:

Mr. Macintosh website: Provides direct download links for macOS installers
Apple Support documentation: Official guides and troubleshooting steps
TidBITS articles: Solutions for expired certificate issues

Conclusion

Creating a bootable macOS USB installer is a straightforward process using Apple’s createinstallmedia command. Whether you’re running the latest Sequoia or working with legacy systems, having a reliable bootable installer is essential for system maintenance and deployment. Keep your bootable installers updated and test them regularly to ensure they work when needed.

This method works across all supported Mac hardware and provides the most reliable way to perform clean macOS installations or system recovery operations.