In order to fix this issue and make VirtualBox full screen, you should install VirtualBox Guest Additions on the guest OS.

If you try to enter the full screen mode by clicking View > Full screen mode in the VM window or by pressing the combination of the VirtualBox host key and F ( Right Ctrl + F in this case), the guest OS screen will not be stretched to the size of your display and resolution will not be increased. For example, in our case the resolution of the monitor is 1920x1080 and the maximum resolution in the Windows 10 guest settings is 1600x1200 (available resolution settings of the guest OS are not for widescreen displays, as you can see). If you go to Windows 10 display settings (right click the desktop and select Display settings in the context menu), you can increase the guest OS resolution, but you still have no ability to switch the full screen mode on. You can also enable 2D and 3D acceleration. It is recommended that you set 128 MB of video memory, as when a video mode with higher resolution is used, more video memory is needed. If you try to maximize the VirtualBox VM window right after installing Windows 10 on a VirtualBox VM, the size of the guest OS user interface is not increased (see the screenshot below).Ĭheck the amount of video memory you have in the virtual machine settings. As you recall, VirtualBox is installed on the host OS running on a host machine (a physical machine) and the guest OS is the operating system running on a VM. You can disable the internet connection or set up a virtual network adapter for a VM in the Host Only mode to allow network communication only between host and guest systems, and deny connecting the Windows 10 guest to external networks, including the internet. If security is a concern for you, running Windows 10 as a virtual machine (VM) on VirtualBox is a good idea. How to Make VirtualBox Full Screen for Windows 10 Guests

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