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I am not sure why this is such a crazy hard problem to find a solution for, but I have two machines: a pc and a MacBook Pro running Catalina. I have recently had to rebuild my PC and lost my old Windows 10 install USB (which as an aside, was created in the days when Bootcamp created bootable USBs) and now I must create another one. Here is the problem, every solution I have tried so far as both not worked and taken 2+ hours to find out that it didn't work.

Has someone successfully created a Windows 10 bootable install USB on macOS Catalina? Please let me know which steps you took. Thanks in advance!

Also, yes, I have googled this and 99% of the solutions either (a) use Bootcamp (not an option) or (b) are geared towards dual-booting macOS & Windows which is not my intent either. Just a quick and simple bootable install USB for a separate Windows machine.

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  • Would it be possible to use etcher? (balena.io/etcher) There is a download for MacOS Nov 18, 2019 at 23:36
  • I'll give it a try! Thanks Nov 18, 2019 at 23:49
  • @FredTheDoggy I do get a warning message that there is additionally configuring required for Windows images and then proceeds to recommend me to use Bootcamp Assistant (which is unavailable with Catalina)... Nov 18, 2019 at 23:50
  • Also, it asks for my system password in a non-macos dialogue which is a huge no-go for me. Nov 18, 2019 at 23:51

2 Answers 2

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I had this exact question. I just finished using this tutorial and it worked for me.

For those who do not want to watch the video (although highly recommended).

  1. Download the ISO you want to use. Open the terminal (in /Applications/Utilities).

  2. cd /path/to/iso to drive in to folder or cd .. to go back the path.

    Convert .iso to .img using hdiutil:

    hdiutil convert -format UDRW -o /path/to/target.img /path/to/source.iso
    

    Rename if OS X gave it a .dmg file extension:

    mv /path/to/target.img.dmg path/to/target.img
    
  3. Connect USB drive and type diskutil list to find the path.

    diskutil list

  4. Unmount USB drive diskutil unmountDisk (location of Disk).

    diskutil unmountDisk /dev/disk2
    

    diskutil umountDisk

  5. Locate img.

  6. In the terminal, type sudo dd if=(Full location of img file) of=(location of external USB drive) bs=1m

    sudo dd if=/Users/adames729/Downloads/windows10.img of=/dev/disk2 bs=1m
    

    sudo dd

  7. Be patient, it will take about 20-45 minutes.

  8. Once complete, eject by running diskutil eject (location of USB drive)

    diskutil eject /dev/disk2
    

    diskutil eject

Edit with an additional step needed to make the USB bootable.

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  • 1
    I'm using Win10_1909_English_x64.iso The latest download from Microsoft, onto a USB, but no matter what I do I'm still getting missing bootmgr. The same for the image on the DVD. Even when I change the boot device sequence. No matter. Missing bootmgr Nov 28, 2019 at 8:57
  • 7
    may I know what's the purpose of converting the ISO file into IMG? How is it being used?
    – Liren Yeo
    Dec 21, 2019 at 15:58
  • Do we really need to set the path to the iso file and not the path to the img file?
    – MadMaxAPP
    Jan 3, 2020 at 14:55
  • @MadMaxAPP you want to use the img not the iso. It's just a typo
    – Plays2
    Jan 16, 2020 at 19:09
  • This option while did work and boot - did not allow me to copy over intel rapid storage tech drivers to the USB. The resultant USB is in Universal RAW filesystem format - which is readonly in macos.
    – PathToLife
    May 26 at 23:49
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This answer needs an update because the latest Windows 10 ISO image is over 5GB, which results in the install.wim in ISO image larger than 4GB. Why this could be an issue? From my test, only FAT32 is supposed to work on Mac. If you want to burn latest Windows 10 ISO, you have to mount the ISO and split the install.wim into small pieces. A lot of online tutorials talking about this.

You can do this with wimlib (split .wim file) and rync (copy files to usb) command to get this done. And there is no need to convert iso to img.

Another possible solution is UUByte ISO Editor (Mac version) , a premium software for creating Windows bootable USB along with other editing features. With the latest update, you don't have to do any additional settings with large Windows 10 ISO. It supports macOS Catalina and Big Sur.

P.S I made a Windows 10 bootable USB on Catalina in less than 2 minutes and successfully installed Windows 10 on my old laptop. My case items:

  • Win10_20H2_English_x64.iso (5.73GB)
  • macOS Catalina 10.15.5 SanDisk
  • SanDisk 32GB USB 3.0 Drive

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