How to Create a Bootable Windows 10 USB Drive on Mac

Creating a bootable Windows 10 USB drive on a Mac is a straightforward process. This method is especially useful if you don’t have access to a Windows PC. Follow the step-by-step guide below to create your bootable USB drive.

Prerequisites:
Before you begin, make sure you have the following:

• USB Flash Drive: A USB drive with at least 8GB of storage. Backup any important data as this process will erase all contents of the drive.
• Windows 10 ISO File: Download the official Windows 10 ISO file from Microsoft’s website and select the appropriate version (32-bit or 64-bit) for your device.

Step-by-Step Guide

Step 1: Download the Windows 10 ISO File

• Visit Microsoft’s official website and download the correct version of Windows 10 for your system.

Step 2: Insert the USB Drive

• Plug your USB flash drive into your Mac.

Step 3: Mount the Windows 10 ISO File

• Double-click the downloaded ISO file to mount it.
• Once mounted, you should see a new volume named something like CCCOMA_X64FRE_EN-US_DV9 in the Finder’s left-hand panel under “Locations.”

Step 4: Format the USB Drive Using Disk Utility

1. Open Disk Utility (search for it using Spotlight Cmd + Space and type “Disk Utility”).
2. Click on View in the top-left menu and select Show All Devices.
3. Select your USB drive from the External section.
4. Click Erase (top-right corner).
5. In the pop-up window, enter a name for the drive (e.g., WIN10) and select:
   • Format: MS-DOS (FAT32)
   • Scheme: Master Boot Record (MBR)
6. Click Erase to format the drive.

Step 5: Copy Windows Installation Files

1. Open the formatted USB drive (WIN10).
2. Also, open the mounted Windows ISO volume (CCCOMA_X64FRE_EN-US_DV9).
3. Copy all files and folders from the ISO to the USB except the sources folder.

Step 6: Handle the “sources” Folder Separately

1. Inside the USB (WIN10), create a new folder named sources.
2. Copy everything from the sources folder of CCCOMA_X64FRE_EN-US_DV9 to the sources folder on WIN10, exceptinstall.wim.
   • The install.wim file is larger than 4GB and cannot be copied to a FAT32-formatted drive.

Step 7: Split install.wim File

Since FAT32 cannot store files larger than 4GB, we need to split the install.wim file into smaller chunks.

Install Necessary Tools

1. Install Homebrew (if you haven’t already) by running the following command in Terminal:/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
2. Install wimlib:brew install wimlib

Split the install.wim File

Run the following command in Terminal (adjust the path as needed):

wimlib-imagex split /Volumes/CCCOMA_X64FRE_EN-US_DV9/sources/install.wim /Volumes/WIN10/sources/install.swm 4000

• This command splits the install.wim file into multiple parts (install.swm, install2.swm, etc.), each 4GB or smaller.
• Instead of manually typing the paths, you can drag the file or folder into the Terminal window to ensure the correct path is set.

Step 8: Verify the Bootable USB Drive

1. Open the sources folder inside the WIN10 USB drive.
2. You should see install.swm and install2.swm instead of the original install.wim.
3. If these files exist, congratulations! Your USB drive is now bootable and ready to install Windows 10.

Conclusion:
By following these steps, you can successfully create a bootable Windows 10 USB drive using a Mac. This method is useful when installing Windows on a PC without access to a Windows machine. If you run into any issues, double-check your file paths and ensure the install.wim file is properly split.

You are now ready to install Windows 10 from your bootable USB drive!