How to Install macOS From USB

Yusuf Limalia Updated 20-12-2018

As you may know, you can reinstall macOS on your computer via the internet recovery. But did you know that you can create a bootable USB drive to install macOS from? This will let you boot your Mac from a different source if it won’t work normally, and makes installs on multiple machines easy.


Let’s see how to do this.

Choosing a USB Flash Drive for Installing macOS

USB flash drives are cheaper than ever, so you won’t have to spend much for this task. However, make sure to buy a name-brand flash drive (like SanDisk, Kingston, or PNY) from a reputable store. Stay away from super-cheap drives with suspiciously high storage on sites like eBay.

These drives have their firmware hacked to report a false size to your operating system. Not only will the transfer speeds be painfully slow, but using them may also result in loss of data or even a damaged USB port.

Fake USB Flash Drives on eBay

Also, check to see what ports you have on your Mac. The 12″ MacBook has a single USB-C port, while MacBook Pro models from 2016 and later feature USB-C ports exclusively. Fortunately, there are USB-C drives available, or you can use a USB-C to USB-A adapter.


It’s best to go with a USB 3.0 drive, with a minimum size of 16GB. The Samsung BAR Plus is good overall value for the money; we’ve highlighted the fastest USB 3.0 drives you can buy for more options.

Samsung BAR Plus 32GB - 200MB/s USB 3.1 Flash Drive Titan Gray (MUF-32BE4/AM) Samsung BAR Plus 32GB - 200MB/s USB 3.1 Flash Drive Titan Gray (MUF-32BE4/AM) Buy Now On Amazon $8.73

Formatting Your USB Flash Drive

You can only create a bootable installer for macOS on a Mac. If you’re using a flash drive that already has data on it, make sure to back up any important files as you’re going to erase everything in a moment.

Open Finder. Navigate to Applications > Utilities, and open up Disk Utility. You should see your flash drive under the External section in the left pane. After selecting it, click on the Erase button along the top.


Choose a friendly name (which you’ll use later), and make sure to choose Mac OS Extended (Journaled) for the format. Finally, click Erase and you’re done with this step.

macOS Disk Utility

Downloading the macOS Installer

To download the macOS installer, open the App Store and search for your version of macOS. Click on the Download button if you’re on High Sierra or earlier.

macOS Mojave is slightly different, as it opens up your System Preferences to download the installer. This is because one of the changes in Mojave is a new way of installing updates.


In either case, once the installer opens, quit it without continuing the installation.


Creating a Bootable USB Using Terminal

Terminal is the easiest way to create your bootable USB drive. Just replace the MyVolume portion of the command with the name you gave your drive in the Disk Utility step above.

Take note that the commands differ slightly for creating Mojave and High Sierra installers on older versions of macOS.


Mojave installer on Mojave or High Sierra:

sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume

Mojave installer on Sierra or earlier:

sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\

High Sierra installer on High Sierra:

sudo /Applications/Install\ macOS\ High\ --volume /Volumes/MyVolume

High Sierra installer on Sierra or earlier:

sudo /Applications/Install\ macOS\ High\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ High\


sudo /Applications/Install\ macOS\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\

El Capitan:

sudo /Applications/Install\ OS\ X\ El\ --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\

Copy and paste the command you need above into your Terminal window and press the Return key. After entering your password, confirm you want to erase the USB drive by typing Y followed by Return.

Terminal will now erase and create your bootable USB drive, ready for you to boot from.


Creating a Bootable USB Using DiskMaker X

If you’re not a fan of using Terminal, you can try a third-party app designed specifically for creating a bootable macOS USB drive. After downloading your macOS version of choice as detailed above, you can download and install DiskMaker X.


Due to its updated security, macOS Mojave has some additional steps required if you’d like to use DiskMaker X. The developers recommend reversing these changes after you’ve made your USB drive if you’re not planning on using the app in the future.

Navigate to System Preferences > Security & Privacy > Privacy > Accessibility. To make changes, click the lock icon at the bottom and enter your credentials.

Then click on the Plus button, navigate to the Applications folder, select DiskMaker X, and click open. DiskMaker X should now appear on the list.

Mojave Privacy Preferences

As soon as you launch DiskMaker X, it will prompt you to confirm the macOS installer you’ve downloaded.

The next prompt shows one of the advantages of DiskMaker X in that you can create a multi-installation disk. This means that you can create a few partitions on your USB drive and have a different macOS installer on each partition.

If you would rather create a single install disk, select Erase All Disk. Lastly, confirm that you’d like to erase everything on the USB drive.


DiskMaker will continue to create your disk in the background and update you on its progress. After a few minutes, DiskMaker X will notify you that your boot disk is ready and give you some instructions on how to use it.

Booting Your Mac From a USB Drive

Now if you find yourself in a sticky situation where your Mac isn’t booting, or you want to do a fresh install of macOS, you have a solution. You can boot from your USB drive and not have to download the macOS installer again. This will come in handy for fixing the “macOS could not be installed” error How to Fix the macOS Could Not Be Installed on Your Computer Error Seeing the "macOS could not be installed on your computer" error when you try to update? Here's how to fix this macOS error. Read More .

Simply plug your created USB drive into an open USB port on your Mac. Power on the system, or restart it if it’s already on. Immediately press and hold the Option (Alt) key on your keyboard when it starts booting.

You should now see an option to select your USB drive as a startup disk. After selecting it, your system will boot off your USB drive and you’ll be taken to the macOS Utilities screen.


Some wireless keyboards may not work at this point. If you’re having difficulty, plug in a wired keyboard instead. If you don’t see your USB drive as one of the startup options, try a different USB port.

Using Your Bootable macOS USB

From the macOS Utilities screen, you can perform a fresh install of macOS, restore from a Time Machine backup, or access tools like Disk Utility. You can also use your USB drive to upgrade macOS to the latest version. If you need to troubleshoot your Mac without a network connection, this USB drive could be a lifesaver.

Did you know you could also install multiple operating systems on a USB stick How to Install Multiple Bootable Operating Systems on a USB Stick Want to install and/or run multiple operating systems from a single bootable USB stick? You can with these tools. Read More ? We show you how:

Image Credit: karandaev/Depositphotos

Related topics: Install Software, macOS High Sierra, macOS Mojave, USB Drive.

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  1. Craig
    February 11, 2020 at 1:01 am

    I've followed your tutorial without problems. An issue I'm running into is applying Mac OS updates to upgrade the OS installed on an external USB flash drive. The updates begin & complete with an error. Is there a tutorial to install Mac OS updates to Mac OS installed on an external USB drive?

  2. Wiley1
    May 11, 2018 at 3:37 pm

    The experience of building the USB with DiskMaker_X_7 was painless. I am now able to boot to a screen with two icons like the one shown in this article. At this point, I select the USB drive that is named "Install OS X High Sierra" and that takes me to the menu with 4 choices. When I go into Disk Utilities, I am able to re-format the 500GB HD in the iMac and it automatically creates a new volume. I named my volume "Abyss".

    Then I return to the 4-choice menu and select "Install MacOS", and click the Continue button. The Continue button turns gray -- forever.

    Yes, I have verified that this iMac is eligible to use High Sierra.

    What could be wrong? Is it possible that I need a newer OS X Base System? Can that be upgraded?

  3. Mohamed
    June 20, 2016 at 8:10 am

    Cant boot my iMac, only in recovery mode...and reinstalling OS X from the web is a headache since my internet connection is slow and unstable....Creating USB bootable right now, fingers crossed! thanks for the help

  4. kong
    May 14, 2016 at 3:13 am


    I have the same problem which is why i search and get to here. Seem that USB bootable os can help. Anyone can help to answer Nazy.

  5. nazy
    May 10, 2016 at 10:46 am

    My mac is not working and I cant log in, and i have low storage to reinstall osx using recovery system.and i have tried others way but it didnt help. so I want to know if I download El capitan using another computer, which is not a mac,and also from the sites that have a link for downloading, what else should i do, to be able use it as a start up disk on my mac ?

    pleeeeease help!

  6. Anonymous
    October 29, 2015 at 5:58 am