How to Dual-Boot Windows and macOS on a Mac

By Melanie Pinola 19 January 2018

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.

How to Dual Boot Mac OS X El Capitan and Windows 10

It’s not often that computer users get the best of both worlds. For the most part, you’re either a PC person or a Mac person, and “never the twain shall meet.” But for those of us who actually prefer to straddle the dividing line between PC and Mac, there’s a method by which you can have your proverbial cake and eat it too.

It’s called dual booting, and it lets you jump back and forth on your Mac between operating systems with dexterous ease, not even requiring you to get up out of your comfy office chair to switch to another computer. Here’s how it works.

What You’ll Need

Before you get all excited and begin your charge, there are a few things to take into consideration. Just as no battle is ever won without first equipping yourself with the right stuff to pull out a victory, no serious computer makeover can ever be accomplished without having a few necessary tools in your arsenal. This is what you’ll need:

• Perform a full backup of your data so nothing’s lost in the formatting and partitioning of your hard drive. You should already have a system in place to back up your data. If not, don’t waste time browbeating yourself. Get busy backing up your data, then move on to the next step.
• Your Mac’s keyboard, mouse, or trackpad. A USB keyboard and mouse can be used instead if the original equipment is no longer in your custody. Bear in mind that you may run into trouble during Windows installation if you’re using an Apple mouse or the Apple touchpad plugged directly into your Mac.
• A Mac computer that will support Windows 10. Go here to see if your Mac makes the cut.
• A Mac with a bare minimum of 2GB of RAM.
• Plenty of space in your hard drive, enough to fit both operating systems. At minimum, you should have at least 55GB of free space in your partition for the 64-bit version of Windows 10. If you’ve got more room than that, even better.
• A 16GB USB flash drive, which is required for some Mac models to install updated drivers.
• Installation discs for Windows and OS X. Some Macs will allow you to install Windows from a USB flash drive that contains a Windows 10 ISO image downloaded from Microsoft, which is why you may need the aforementioned 16GB USB flash drive. You can download Windows 10 here.

• Internet access and an administrator account in OS X.
• Enough computer savvy to ensure you don’t make a mess of your system. You don’t need to be a guru to configure your Mac for dual booting, but you should be able to follow the steps without having to constantly ring up your computer pals to ask for clarification. If you find yourself reaching for the phone or scratching your head every five seconds, consider getting a pro involved. Or check with the experts in the NotebookReview forum.

Putting Boot Camp Assistant to Work

If you own a Mac that’s even a few years old, it came pre-loaded with a program called Boot Camp Assistant, which was intended to make setting up a dual boot scenario possible.

Depending on which version of Windows you want to use, you may require a different version of Boot Camp Assistant. For the purposes of this article, where we’re focusing on dual booting into Windows 10, you’ll need to be running OS X Yosemite or later on your Mac. In this case, “or later” refers to the newly available OS X El Capitan. The version of Boot Camp Assistant that comes with Yosemite and El Capitan supports the 64-bit version of Windows 10. Go here for separate instructions on how to dual boot Windows 7 on your Mac, and here for Windows 8.

Installing Windows 10 on Your Mac

Follow the steps below to install a new copy of Windows 10. If you already have an earlier version of Windows on your Mac but want to upgrade to Windows 10, skip this entire section and scroll down to Upgrading Windows.

• Check for any OS X updates you still need to install. Be sure to log into your Mac administrator account and log out any other users. While you’re at it, quit out of any running apps. Check here to ensure you’re up to date on any necessary updates.

• Read over the documentation for Windows 10 to ensure your Mac has the right kind of processor to make it all fly. Then, check your Mac’s System Information to make sure you’re equipped.

• Create an ISO disk image if the version of Windows 10 you’re installing came on a disk. If you’re working off Windows from a USB flash drive, download an ISO from Microsoft directly. You can get that here.
• Launch Boot Camp Assistant. You’ll find it in your Utilities folder. If you’re prompted to do so, plug in your USB flash drive.
• Once Boot Camp is done doing its thing, your Mac will restart and launch the Windows installer automatically. You’ll then be prompted to select where you want to install Windows. Pick the partition labeled BOOTCAMP and then select the Format option. We recommend dedicating at least 30GB of space for the Windows side, although if you’re unsure you can always refer to your accompanying Windows documentation to see just how much space you’ll need. There’s also the option to split the drive evenly down the middle. Take into account how you plan to use Windows 10 and add space accordingly if you plan on using it a lot for games and other intensive applications.

• Continue following the Windows configuration and installation prompts.
• Reboot your Mac into your desired OS by using the Startup Disk preference pane in OSX, or the Boot Camp system tray icon in Windows.

Then What?

Follow all onscreen instructions through to completion of setup. You might encounter a message telling you that the software you’re installing hasn’t passed Windows Logo testing. If so, just click Continue Anyway.

Your Mac will once again restart. Follow all and any instructions to finalize installation.

If you happen to experience any trouble with Windows installation, pay a visit to Apple.com’s Boot Camp Support page to troubleshoot and fix any issues.

Upgrading Windows

To upgrade an already existing version of Windows on your Mac to Windows 10, first determine if the version of Windows you’re currently running is 64-bit or 32-bit and follow the appropriate steps below.

Upgrading 64-bit Windows

• If you’re running Windows 8 and want to upgrade to Windows 10, you’ll first have to upgrade to Windows 8.1 to make the leap.
• Ensure you have at minimum 10GB of free space on your Windows partition.
• Reboot your Mac in OS X and check for any software updates you’ll need.
• Next, reboot your Mac into the existing version of Windows you have installed and download any required Windows OS updates.
• Upgrade your current version of Windows to Windows 10.
• Next, make sure you have all Windows support software drivers for Boot Camp are up to date. Then log into Windows 10.

Upgrading 32-bit Windows

• Access your Windows partition and back up any files you don’t want to lose.
• Launch Boot Camp Assistant and remove the existing Windows partition.
• Next, follow all the steps outlined in Installing Windows 10 on Your Mac (above).

Toggling Between OS X and Windows

Once everything’s been installed correctly, you’ll be able to start your Mac in either OS X or Windows.

Switching from one operating system to another is as easy as rebooting and holding down the Option (Alt) key during restart to pick your desired OS.

Removing with Ease

If you’re not a fan of Windows 10 and you want to make it go away, doing so is easy. Simply launch Boot Camp again, check the option to remove Windows, and click Continue. If you click Restore on the next screen you see, you will completely wipe the newly installed Windows partition.

Dual-Boot macOS on a drive with Windows 10 already installed (Shared Drive)

One of the things holding back a potential hackintosher from trying to hackintosh or install macOS on their PC is that they have only one hard drive and that hard drive already has Windows installed on it with no secondary backup or second drive to spare. There is actually a way to install macOS on a drive that already has Windows installed on it without having to delete Windows, but this will only work if the Windows disk is GPT formatted.

Step 1: Verify GPT Partition Type

1. Install MiniTool Partition Wizard Free Edition
2. Open MiniTool Partition Wizard
3. Verify your Disk is GPT partitioned and has an EFI system partition. If the drive is formatted as MBR you are out of luck and can’t follow this guide. You’re only option would be to reinstall Windows in UEFI mode or install macOS first.

Step 2: Resize Windows EFI for macOS

When a hard drive is formatted in Windows or macOS it creates a hidden partition called “EFI” macOS requires an EFI partition of 200MB in size to install macOS, but if you’re drive was formatted using Windows that EFI partition is only 100MB in size. So we need to increase the size of the partition to 200MB.

To increase the size of the EFI partition we need to take away space from the partition before or the partition after it. Everyone’s partition layout will look a little different.

As you can see in the image above to the left of my EFI partition I have the Windows Recovery partition and to my right I have the System Reserved partition / (Other) 16 MB. I’m not able to get enough free space from the Recovery partition or the small 16MB system reserved partition to reach 200MB. So my only option is to delete the System Reserved partition as it’s not as important to have as the Recovery partition. The reason I’m going to delete the System Reserved partition is because the EFI partition needs to be next to a partition like the C: partition which we can take space away from and I can’t do that the with System Reserved partition wedged between. I also can’t add space to the System Reserved partition and then add that space to the EFI so my only option is to delete. If your EFI partition is already next to a partition you can take away space from like a C: partition then you don’t need to delete.

1. Right-click (Other) 16MB and select Delete
2. Right-click C: and select Move/Resize
3. Change the GB labels to MB labels to make resizing easier
4. Subtract enough space from Partition Size: to make Unallocated Space Before: 100.00 MB (For example I started out with Unallocated Space Before: 16.00 MB I subtracted 84.00 from Partition Size: I then set Unallocated Space After: 0.00 which automatically moves the space to Unallocated Space Before:)
5. Click OK when done (You should now have 100 MB unallocated)
6. Right-click the 100MB EFI partition and select Move/Resize
7. Verify 200MB size change and click OK
8. Right-click C: and select Split
9. Set the partition size for macOS and click OK
10. Right-click new partition and select Format
11. Set File System: Fat32 and click OK
12. Click Apply at the top left of Partition Wizard
13. Click Restart Now on prompt (MiniTools Partition Wizard will apply format changes to the drive on restart and then restart again brining you back into Windows. As it does this don’t touch anything.)

Step 1: Access macOS

To even make a flash drive with a Mac OS installer on it you will first need either a. Access to a Mac or b. A virtual machine running macOS. If you do not have a Mac or one to borrow then create a virtual machine running macOS using one of the two links below depending on whether you are using Intel or AMD as your CPU/Processor.

Step 2: Make a macOS High Sierra Hackintosh

Before you begin installing Mac OS there are two important things you need to know before you begin. When you first boot the macOS flash drive installer and open Disk Utility, you will select the Fat32 hackintosh partition you made in Step 1.11 and click Erase. You will then set Format: Mac OS Extended (Journeled)

The second important part comes when you boot Mac OS on your hackintosh for the first time and merge the EFI folders of your boot drive EFI folder with the flash drive EFI, which you’ll do once you reach this step. I would make a .zip backup of your boot drive EFI before the merge just in case you mess things up when you merge the flash drive’s EFI folder with the boot drive EFI folder.

Now that we have access to macOS we will now create a flash drive installer containing macOS install files and then install macOS. Based on what CPU/Processor you are using following the full guide below and then return to this one once you have macOS running. Just os you know you will need to completely wipe the drive you are using in order to format as GUID using Disk Utility. Also after macOS keep the flash drive the way it is as you will need it later.

Step 3: Dual-Boot Mac OS and Windows 10 using Clover

The last step is be able to boot boot Windows 10 and Mac OS using Clover EFI Bootloader to do that follow Step 5 & 6 of this guide: Hackintosh Dual Boot Windows 10 and macOS High Sierra (Same Drive)