This article is part of a series on how to burn the Windows 10 disk image on a USB key using your Mac computer. As there is no one-size-fits-all way of doing this procedure, I divided this series into four articles. This one shows how to burn the Windows ISO to USB by copying its content to a pen drive. 

Overview: Burning a Windows 10 disc image to USB on macOS Big Sur.

This article provides an introduction to this topic, as well as the limitations of each method presented.

Method One: Use the macOS Boot Camp Assistant to burn the Windows ISO to USB.

This article provides a way of burning the Windows image that relies on the use of a macOS computer as the host.

Method Two: Burn a Windows 10 ISO image by mounting it in macOS and copy its content to USB, which is the present article.

Method Three: Use the live version of a Linux distribution to create a bootable Windows 10 USB drive. 

This article provides another way of doing this procedure that is compatible with all operating systems.

As you can see, there are several ways of burning a Windows ISO to USB from your Mac computer. The choice between one method or another will depend on several factors. The size of your Windows ISO file, whether you intend on booting Windows on a mac or pc, and whether or not you wish to use Linux are all aspects to consider. 

Burning the Windows ISO to USB by mounting it and copying its content

This way to burn the Windows ISO to USB is straightforward but somewhat inconvenient. Indeed, it requires getting a hold of a Windows 10 ISO file with a size of less than 4GB. There is a very good reason for this maximum file size. To create a bootable USB that is compatible with both Mac and Windows operating systems, you need to format the target pen drive using FAT32. This format, with its maximal allowed size of 4GB, can be considered obsolete as the modern USB keys we use nowadays can easily reach 128GB or more. FAT32 is only one of the many formats available during the formatting process, and people usually prefer to use an alternative such as exFAT.

However, trying to find a version of Windows 10 with a size of 4 GB or less can cause quite a headache. Up until sometime in 2018, it was possible to get an official Windows 10 disk image from Microsoft that was under 4gb. As of August 2019 however, all versions found on are over 4gb. You thus have to find a Windows 10 ISO file under 4gb from somewhere else. Note however that whatever version you stumble cross will also probably be out of date, seeing as all regular 2019 versions are more voluminous than 4gb. If you find no version under 4GB, or if the one you find doesn’t suit your needs, use one of the other methods presented earlier.

Where to find a Windows 10 ISO image under 4 GB?

Thankfully, there exists an online database that provides us with a way to burn the Windows ISO to USB. On it, you will find Windows disc image alternatives, including many Windows 7, 8 and 10 versions. Go to, then select a disk image which meets the 4GB requirements. Your release will be out of date, but nothing which cannot be fixed on the actual Windows operating system once you have installed it on your computer. After all, if there is one thing Windows is known for, it’s its insistence on imposing frequent and automatic updates.

Note also that unfortunately, you won’t be able to burn the Windows ISO to USB using this method if the disc image is anything over 4GB, even something like 4.02GB.

For the sake of this tutorial, I tried hard to find a Windows 10 disk image that met the requirements. I finally was able to find a single one, Microsoft Windows 10 N 64-bit version, which you can find here ( However, I don’t recommend using it as your full time operating system. Burning this Windows ISO to USB will result in an operating system that is quite lacking. Indeed, it comes without media-related applications such as the camera and Windows Media Player. Furthermore, it requires a specific product key that exists only for the N-Edition.

Once you’ve found a Windows disk image that answers the file size requirement, you can begin the procedure to burn it on a bootable USB key.

The procedure

You will need:

  • A USB stick with a capacity of 4GB (it can have a higher capacity than that, but the extra storage space will be unusable)
  • A Windows 10 ISO file with a total size of less than 4GB
  • Access to the Terminal and Finder


Download your ISO file and remember its location.

Insert the USB key into your Mac.

Access the terminal by doing a spotlight search for “Terminal.”

Identify your computer’s drives to find which one is linked to your USB key. To do so, enter the following command:

diskutil list

Steps used to burn a Windows ISO to USB from macOS Mojave

You will find a list of disks; in the example above, you can see that my USB key is the external drive located on disc 3. You can identify your pen drive by the following:

When it says “(external, physical),” it means that it is an external drive such as a pen drive or external hard drive. If you see the words “internal,” “synthesized,” or “disk image,” it is not a pen drive.

It is best to have a single USB drive inserted. Otherwise, look for the particularities of the USB you wish to use to burn your ISO file. Its size is the biggest giveaway.

Format your USB stick and mount it as a volume named “Windows10”. To do so, type:

diskutil eraseDisk MS-DOS "WINDOWS10" MBR <diskNUMBER>

Steps used to burn a Windows ISO to USB from macOS Mojave

Where <diskNUMBER> is the disk linked to your pen drive. In the example below, my disk is disk3. A word of caution: Unlike with regular applications, the command line will never ask you to confirm whether or not you wish to format the disk you chose. So be sure that you are indeed writing down the correct disk as otherwise, you might end up trying to format your internal drive.

The name “WINDOWS10” is not mandatory; if you’d rather call your pen drive something else you can do so. Also, for those curious about what “MBR” does: it is a command that stands for Master Boot Record. It is used by Windows and Linux to identify how and where an operating system is located and allows the OS to be booted properly.

The process should be over pretty quickly. Once the formatting complete, you will see “Mounting disk,” followed by “Finished erase on <diskNUMBER>.”

Steps used to burn a Windows ISO to USB from macOS Mojave

Using the Finder, open your Windows 10 ISO file. Take note of the name the mounted volume displays (you can find the name under the volume icon on the desktop).

In this example, the name of my mounted volume is “J_CCSNA_X64FRE_EN-US_DV5”.

Steps used to burn a Windows ISO to USB from macOS Mojave

You will now have to copy the volume’s content on your USB drive. Note that for this, we will use the command line (thus why we had to get the name of the volume earlier.

Do not use the Finder to try and copy the content directly from the mounted volume to your USB key. Even though it is tempting to do so, you might get an error message.

We will use the “cp” and “-rp” commands. Type the following:

cp -rp /Volumes/<YOURVOLUMENAME>/* /Volumes/WINDOWS10/

Then press Enter. In this example, my command would look like this: “cp -rp /Volumes/J_CCSNA_X64FRE_EN-US_DV5/* /Volumes/WINDOWS10/”.

Do not forget to include the asterisk after your volume’s name, as you use it as a “directory wildcard.” This wildcard directory wildcard ensures that you will be able to copy every directory present in your volume.

You will see a new blank line appearing after the command. This is normal, and you will have no other indication of the “copy and paste” process. You will not be able to see how long this will take, which files (or their quantity) have been copied or what percentage of the task has been completed. The step will take some time, so be patient.

Once the process is complete, you can exit the terminal. You can then eject the USB key by using the Finder or by moving the desktop volume to the Trash.

You can now use the pen drive to boot Windows from any pc!

Owner and content creator behind Geeky girl and blogger based in Montreal, Canada. Chocolate and nature lover (in that order). View all posts by Larryssa →

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