I'm running 10.6.8 and when I try to use BootCamp, it tells me I need "at least 10GB of free space", which is interesting since I have 21GB of free space. However, trying to fix this issue has seemed pointless at this rate and I remember there used to be way to create bootable USBs using only Disk Utility during the Vista era. I had tried converting my .iso to .dmg and mounting them and 'burning' them to the flash drive, but nothing has seemed to work. All the tutorials I have found online use BootCamp, which is what I want to stay away from since it does not work for me.

So is there a way to do this? And what is the recommended file type .iso, .img, or .dmg to be used? Should it be mounted or unmounted when I try to 'burn' it?

  • see support.apple.com/en-us/HT204048 for which Macs can support Win 8 - essentially, anything before 2011 won't do it. You also need Win 8 64, not 32
    – Tetsujin
    Jan 19, 2015 at 18:51
  • My macbook is from late 2011. And I have a Windows 8 64-bit iso. I tried something new now and I keep getting "Could not validate source - error 254", with no idea how to fix that now. However, I thinking fixing my new issue would actually allow me to create the fully bootable usb.
    – Graham S.
    Jan 19, 2015 at 18:57
  • Are you creating the USB in Bootcamp? It won't work otherwise… that's why the error 254
    – Tetsujin
    Jan 19, 2015 at 19:12
  • @Tetsujin: Actually you can run windows 8.1 on macs older than 2011. My iMac is Mid 2007 and is running windows 8.1 without a problem. See screen shot of desktop. Jan 19, 2015 at 20:01
  • No, I am creating it in Disk Utility. Is it for certain that it can only be done in BootCamp? I had done this before with a copy of Windows Vista a few years ago using only Disk Utility and it had worked.
    – Graham S.
    Jan 19, 2015 at 20:02

7 Answers 7


None of the answers got it right.
This is how you do it — without BootCamp:

  • Get/download a Windows ISO image file.
  • Your USB flash drive should have at least 8GB.
  • Plug it in and format/erase it using Disk Utility (under Applications/Utilities)
    • CAUTION: Make sure you select the correct drive! Then click erase.
    • Select MS-DOS (FAT) for the Format.
      (If your drive is above 32GB, you might need to select ExFAT instead.)
    • Select Master Boot Record for the Scheme.
      (This is the one used for Windows partitions.)
    • Click erase. enter image description here
  • Open Terminal and run command: diskutil list
    From the output, find out the name of the USB drive. It should be something like /dev/diskX. X is the number of the drive. For me, it's /dev/disk2. It might be different on your Mac.
  • Then type command: diskutil unmountDisk /dev/disk2
    It should print something like this: Unmount of all volumes on disk2 was successful.
  • Then type: sudo dd if=/path/to/win-iso-file of=/dev/disk2 bs=1m
    (This will ask for your Mac password. Enter it and hit return.)
    • /path/to/win-iso-file is the full path of the ISO image. Just drag/drop it on terminal after if= and it will print the full path.
  • The process will start but there will be no output for a while. It might take 10 to 45 minutes. Be patient! (You can press Ctrl+T to see the bytes transferred so far.)
  • Once it's complete, it will output records in/out and bytes transferred.
  • Type: diskutil eject /dev/disk2
  • Now, re-plug the USB drive and check its contents. It should have files and folders but especially a setup.exe and an autorun.inf file. enter image description here
  • Done.
  • 1
    This didn't create a "bootable" USB for me, I'm guessing older boxes can't handle newer boot schemes, ended up having to use rufus on a windows box then it worked...
    – rogerdpack
    Jan 15, 2019 at 14:34
  • This does create a bootable USB, but I can't install Windows on a new machine with it. It says "media driver missing". Try use Rufus on Windows to create the bootable USB instead.
    – thyu
    Aug 18, 2019 at 6:13
  • Didn't boot for me.
    – mixtly87
    Nov 12, 2020 at 23:00

Have you tried using the cross-platform application called "unetbootin"?

Correct me if I'm wrong, but I've been using this method for the past year and a half, and it works quite well. Although, it's a little tedious and involves the CLI/Terminal. You'll have to install the MBR bin files manually with either SysLinux or the ones that are included within the unetbootin.app package contents.

Here is a link to the full instructions from the very popular blog post.

  • 1
    this is for creating a linux bootable USB Oct 19, 2016 at 20:10

UPDATE: Graham try using this answer: Creating A Bootable USB Of Windows 8.1 On OS X?

  • oh jeez, you really do need to use question marks. Mar 3, 2018 at 20:20

Follow the instructions here on creating a bootable USB from a Windows ISO file: http://www.reddit.com/r/mac/comments/2fy3be/by_popular_demand_my_better_than_bootcamp_guide/

Unfortunately, I'm having difficulty finding the original tutorial I used to install Windows 8.1 on a partition on my Mid 2009 MacBook Pro, but here is a similar write-up: http://huguesval.com/blog/2012/02/installing-windows-7-on-a-mac-without-superdrive-with-virtualbox/

Note: This works with the Windows 8.1 Enterprise Trial, which can later be upgraded to a retail copy. https://www.microsoft.com/en-us/evalcenter/evaluate-windows-8-1-enterprise

  • @OnurYıldırım You realize you're asking a question on a 1.5 year-old answer?
    – fsb
    Oct 19, 2016 at 20:26
  • @fsb, right. "with/out bootcamp" is 5+ years old. Oct 19, 2016 at 22:16

BalenaEtcher is an option for ISO images burn.
I found it inside some of Ubuntu's tutorials
It is multiplatform and it works for me very well.


This post needs an update as a few changes has been made in recent years.

UUByte ISO Editor is a quite good alternative to make bootable Windows USB installer on Mac. It is a GUI app and does the job more easily. However, it is a premium software.

BTW, none of the above suggestions are working if the ISO file is larger than 4 GB because of the limitation of FAT32 file system.

And UNetbootin is not able to support Windows 8 ISO.


In order to create usb bootable for win 8.1/10 without any additional software please try this method https://laptoptechgeek.blogspot.com/2018/11/how-to-create-bootable-usb-for-windows.html

  • For that method you need a windows machine. The question is clear about creating a bootable usb using a Mac without bootcamp Dec 9, 2019 at 7:56

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