How to Dual-Boot Windows and macOS on a Mac
Mac vs. Windows. Windows vs. Mac. Why choose when you can get the best of both worlds by dual-booting? Here's how to install Windows on your Mac using Boot Camp so you can jump back and forth between the two operating systems on the same computer.
What You'll Need
Before you start, make sure you have enough space on your hard drive for both Windows and Mac. We recommend at least 30GB for each, but the more space you have, the better. You'll also need a USB flash drive (4GB or larger) and a Windows 10 ISO disk image, which you can download here from Microsoft, and a valid Windows 10 license. Finally, make sure your Mac model can support Windows 10 in Boot Camp--check this list to find out.
Install Windows 10 on Your Mac
In the steps below, we'll use Boot Camp Assistant to create a bootable USB drive and install Windows 10 on a new partition. Then you'll be able to choose which OS you want to use whenever you start the Mac up.
1. Download the Windows 10 ISO disk image from Microsoft using this link. Choose the 64-bit version of Windows. Also, some people, including myself, have gotten an error message if the ISO image is saved to your default Downloads folder, so save the ISO image to your Documents folder or somewhere else to avoid problems.
2. Open Boot Camp Assistant. You'll find this in the Utilities folder or you can hit CMD + Spacebar to search for "Boot Camp Assistant."
3. Click Continue at the Introduction screen.
4. Click Continue again at the Select Tasks screen.
5. Choose the Windows ISO image and select the destination USB drive. Note that the USB drive will be reformatted, so make sure you have a copy of any of the files on it somewhere else before proceeding.
6. Click Continue and then Continue again. Your Mac will format the USB drive and create the Windows installation media.
7. Click Install to accept the partition size for each OS. By default, Windows will have a 32GB partition, but you could also click the Divide Equally button to divide your Mac's hard drive space equally between OS X and Windows.
7. Follow the prompts to finish installing Windows. The Mac will need to restart to complete the process and will automatically boot into Windows 10 when it's done.
Set the Default Startup OS or Toggle Between OS X and Windows
Once you have Windows installed, you can set the default OS that will start each time you boot your Mac. To do this, head to the Startup Disk preference setting in Settings.
Every time the Mac starts, you can also toggle between OS X and Windows by holding down the Option (Alt) key immediately upon startup.