How to Create a Bootable macOS USB Installer: Step-by-Step Guide

Published: May 15, 2025
Last Updated: May 15, 2025
By: macOSUpdate Team

Table of Contents

Introduction

A bootable macOS installer is a USB drive that contains the macOS installation files and can be used to install macOS on any compatible Mac. It's an essential tool for performing clean installations, updating Macs without internet access, or troubleshooting system problems.

This guide will walk you through the process of creating a bootable macOS USB installer that you can use to install or reinstall macOS on any compatible Mac.

macOS Bootable USB Installer Drive

A USB drive converted into a bootable macOS installer

Benefits of a Bootable Installer

Having a bootable macOS installer offers several advantages:

  • Clean installations: Perform a fresh installation of macOS without relying on recovery mode.
  • Multiple Macs: Update several Macs without downloading the installer multiple times.
  • Offline installations: Install macOS on Macs without internet access.
  • Troubleshooting: Boot from the USB to access recovery tools when your Mac won't start normally.
  • Specific versions: Install specific macOS versions that might not be available through regular updates.

Requirements

To create a bootable macOS installer, you'll need:

  • A Mac running macOS Mojave or later
  • A USB flash drive with at least 16GB of storage
  • The macOS installer application (downloaded from the App Store or Apple's website)
  • Administrator access to your Mac

Note: The process will erase all data on your USB drive. Make sure to back up any important files before proceeding.

Preparation

Before creating the bootable installer, you need to download the macOS installer and prepare your USB drive.

Downloading the macOS Installer

You can download the macOS installer from the App Store or Apple's website:

Method 1: App Store (for current and some previous versions)

  1. Open the App Store on your Mac
  2. Search for the macOS version you want (e.g., "macOS Sonoma")
  3. Click "Get" or "Download"
  4. The installer will be downloaded to your Applications folder

Note: Once the download completes, the installer may launch automatically. Quit the installer without proceeding.

Method 2: Direct links from Apple (opens App Store)

Method 3: Apple Support page (for older versions)

For older macOS versions, visit Apple's How to download macOS support page and follow the instructions for your desired version.

Tip: The macOS installer is typically around 12GB in size. Make sure you have enough storage space and a stable internet connection before starting the download.

Preparing the USB Drive

You need to prepare your USB drive by formatting it correctly:

  1. Connect your USB drive to your Mac
  2. Open Disk Utility (from Applications > Utilities)
  3. In the sidebar, select your USB drive (not the volumes under it)
  4. Click the "Erase" button in the toolbar
  5. Set the following options:
    • Name: "macOS Installer" (or any name of your choice)
    • Format: Mac OS Extended (Journaled)
    • Scheme: GUID Partition Map
  6. Click "Erase" to format the drive
  7. When the process completes, click "Done"
Disk Utility formatting USB drive

Formatting the USB drive in Disk Utility

Warning: All data on the USB drive will be erased during formatting. Make sure to back up any important files before proceeding.

Creating the Bootable Installer

Now that you have downloaded the macOS installer and prepared your USB drive, you can create the bootable installer.

Terminal Method (Recommended)

The most reliable way to create a bootable installer is using the createinstallmedia command in Terminal:

  1. Make sure your USB drive is connected and properly formatted
  2. Open Terminal (from Applications > Utilities)
  3. Copy and paste the appropriate command based on your macOS version:
# For macOS Sonoma
sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS\ Installer

# For macOS Ventura
sudo /Applications/Install\ macOS\ Ventura.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS\ Installer

# For macOS Monterey
sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS\ Installer

# For macOS Big Sur
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS\ Installer
  1. Press Return to execute the command
  2. Enter your administrator password when prompted (your keystrokes won't appear as you type)
  3. When asked to confirm that the process will erase the drive, type Y and press Return
  4. Wait for the process to complete (it may take 20-30 minutes)
  5. When you see "Done" in Terminal, the bootable installer has been successfully created

Note: If your USB drive has a different name, replace "macOS Installer" in the command with your drive's name. If your drive name contains spaces, remember to use the backslash before each space as shown in the examples.

Terminal running createinstallmedia command

Terminal showing the createinstallmedia process

Alternative Methods

While the Terminal method is recommended for its reliability, there are third-party tools that can simplify the process:

Using DiskMaker X

  1. Download DiskMaker X from the official website
  2. Install and launch DiskMaker X
  3. Follow the on-screen instructions to select your macOS installer and USB drive
  4. Click "Create the disk" to begin the process

Using Install Disk Creator

  1. Download Install Disk Creator
  2. Launch Install Disk Creator
  3. Select your macOS installer and USB drive
  4. Click "Create Installer" to begin

Tip: Third-party tools may not always be up to date with the latest macOS versions. The Terminal method is guaranteed to work with all versions since it uses Apple's official tool.

Booting from the USB Installer

Once you've created your bootable installer, you can use it to boot any compatible Mac. The process differs depending on whether your Mac has an Intel processor or Apple Silicon.

On Intel-based Macs

  1. Ensure your bootable USB drive is connected to your Mac
  2. Restart or power on your Mac
  3. Immediately press and hold the Option (⌥) key
  4. Continue holding the key until you see the Startup Manager screen
  5. Select your bootable installer (usually labeled "Install macOS [Version]")
  6. Click the arrow or press Return to boot from the installer

On Apple Silicon Macs

  1. Ensure your bootable USB drive is connected to your Mac
  2. Shut down your Mac completely
  3. Press and hold the power button until you see "Loading startup options"
  4. When the startup options appear, select your bootable installer
  5. Click "Continue" to boot from the installer

Note: On Apple Silicon Macs, you may need to lower the security settings in Recovery Mode to boot from external media. To do this, boot into Recovery Mode (power on while holding the power button), select "Options," then go to "Security Policy" and select "Reduced Security."

Troubleshooting

If you see "command not found" when running the createinstallmedia command:

  1. Make sure the macOS installer is in your Applications folder
  2. Verify that you typed the command correctly, including all spaces and backslashes
  3. If you've renamed the installer app, make sure to use the exact name in the command
  4. Try downloading the installer again from the App Store

If your bootable USB doesn't appear in the Startup Manager:

  1. Make sure the USB drive is properly connected directly to your Mac (not through a hub)
  2. Try a different USB port, preferably a USB 2.0 port if available
  3. Reset NVRAM/PRAM: Restart your Mac and immediately press and hold Option + Command + P + R for 20 seconds
  4. Try creating the bootable installer again using the Terminal method
  5. Try using a different USB drive (some drives may not be compatible)

If you see this error when creating the bootable installer:

  1. Delete the existing installer from your Applications folder
  2. Make sure your Mac's date and time are set correctly (System Settings > General > Date & Time)
  3. Download the installer again from the App Store or Apple's website
  4. Restart your Mac before trying again

If the createinstallmedia process seems to be taking too long:

  1. Be patient – the process can take 20-30 minutes, especially with slower USB drives
  2. Look for activity on your USB drive (LED indicator blinking, if available)
  3. If there's no progress after 45 minutes, you can try canceling (Ctrl+C) and starting again
  4. Try using a USB 3.0 drive and port for faster transfer speeds

Frequently Asked Questions

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

Yes, you can use any external storage device, including external hard drives or SSDs. Just be aware that the process will erase all data on the selected drive or partition. If you want to use just a portion of a larger drive, you'll need to create a separate partition for the installer.

How long does the bootable USB installer remain valid?

A bootable macOS installer USB remains valid indefinitely. However, if Apple makes significant security or installation changes in newer releases, there's a small possibility that very old installer drives might not work with future Mac models. For best results, create a new bootable installer whenever you need to install a different macOS version.

Can I have multiple macOS installers on one USB drive?

The standard method described in this guide creates a single-version bootable installer. To have multiple macOS versions available, you would need to create multiple partitions on your USB drive (one for each version) or use specialized third-party tools designed for this purpose, such as Twocanoes Boot Runner.

Can I create a bootable installer on Windows or Linux?

Creating an official macOS installer requires macOS. While there are third-party tools and workarounds for Windows and Linux, they aren't officially supported by Apple and may not work reliably. If you don't have access to a Mac, consider using Apple's Internet Recovery instead, which allows for installation without a bootable drive.

Can I install an older version of macOS using this method?

Yes, you can create bootable installers for older macOS versions that your Mac supports. However, you cannot install versions older than what your Mac originally shipped with. Also, Apple Silicon Macs can only run macOS Big Sur and later.