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.

  • Would it be possible to use etcher? (balena.io/etcher) There is a download for MacOS – FredTheDoggy Nov 18 '19 at 23:36
  • I'll give it a try! Thanks – matt murray Nov 18 '19 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)... – matt murray Nov 18 '19 at 23:50
  • Also, it asks for my system password in a non-macos dialogue which is a huge no-go for me. – matt murray Nov 18 '19 at 23:51

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 – Harry McGovern Nov 28 '19 at 8:57
  • 6
    may I know what's the purpose of converting the ISO file into IMG? How is it being used? – Liren Yeo Dec 21 '19 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 at 14:55
  • @MadMaxAPP you want to use the img not the iso. It's just a typo – Plays2 Jan 16 at 19:09

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