So you’ve been trying to change your Windows 10 screen resolution on your VirtualBox host machine, with no luck. This is when the VirtualBox Guest Addition CD image comes to the rescue. If it is your first time trying to fix your VM screen size, then I highly suggest following the step found in this article, as most users do not need to install the package manually. 

Having to manually install the VirtualBox Guest Addition CD image on your VirtualBox Windows 10 VM might seem cumbersome, but it is a must when all else fails. If you’ve tried to install the Guest Addition CD the usual way and have been unsuccessful, it might be tempting to try to fix the screen display issue by changing the VM Display settings to a scale factor of 200%. However, I do not recommend this “solution” at all. 

The Scale Factor setting, found under the "Display" section of the VirtualBox VM's settings.
The Scale Factor setting, found under the “Display” section of the VM’s settings.

First of all, this a band-aid fix rather than a proper way of ensuring automatically optimized screen resolution across all types of monitors. And second, you will end up with a screen that can look rather unsightly and can put a strain on your eyes (especially if you own a big monitor). 

Instead, I recommend installing the required VirtualBox Guest Addition CD manually. That way, not only will your VM have a window resolution that is pleasing to the eye, but you will also ensure that your VirtualBox application is complete. Indeed, if, when following the instructions below, you realize that you cannot locate the required ISO file to proceed, you will know that your current version of VirtualBox is either obsolete or lacking some key components.   

If you’ve already looked at the instructions and can’t prompt the launch of the VirtualBox Guest Addition CD wizard, then follow the instructions below to manually add the disc image to VirtualBox and make it accessible from your Windows 10 VirtualBox session. 

  • Make sure that your Windows 10 VM session isn’t active.
  • Open the Finder. In the “Applications” menu locate the VirtualBox icon.
The VirtualBox icon on macOS Catalina.
  • Right-click on the icon, then click on “Show Package Contents. 
Browsing the Package Contents of your VirtualBox application will allow you to search for the Guest Addition CD ISO file.
  • Double-click on the “Contents” folder.
The Contents folder of VirtualBox.
  • Double-click on “MacOS”
The MacOS folder of VirtualBox, where the Guest Addition CD is located.
  • Make sure that you can locate the “VBoxGuestAdditions.iso” file. If it isn’t in the folder, it means that your version of VirtualBox isn’t complete. Uninstall it and make sure to download an official release from the VirtualBox website. To do so, go to and click on “OS X hosts” under “VirtualBox 6.1.4 platform packages.” The file should begin downloading immediately. 
Download VirtualBox - make sure to select "OS X hosts"
  • Once you have confirmed that the VirtualBox Guest Addition CD image is present in your VirtualBox application, exit the Finder and open VirtualBox. 
  • In the main VirtualBox menu, click on “File” then on “Virtual Media Manager…” (alternatively, you can use the shortcut key ⌘+d).
Manually installing the Guest Addition CD package via the Virtual Media Manager.
  • In the Virtual Media Manager, click on “Optical disks,” then click on “Add.”
The Virtual Media Manager options - choose Optical disks.
  • Locate the “VBoxGuestAdditions.iso” file. Virtual Box should automatically direct you to the “MacOS” folder within the VirtualBox -> Contents folder. From there, scroll down until you find the ISO file. 
  • Click “Open.” Voila!
The Guest Addition CD ISO file is now installed and ready to be launched from your Windows 10 VM.
  • You can now close the Virtual Media Manager.
  • Now that you’ve manually installed the Guest Additions disk image in VirtualBox, start your Windows 10 VM. 
  • Now simply configure the Guest Additions by following these instructions.

You are now all set! 

Owner and content creator behind Geeky girl and blogger based in Montreal, Canada. Chocolate and nature lover (in that order). View all posts by Larryssa →

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