
So, while in scaled or full screen mode inside VirtualBox installed on Windows, you need to press Right Ctrl + C key combination to exit scaled mode.

In Mac, the default host key is usually Left Command button. In Windows, host key is usually set to Right Ctrl on keyboard. A host key in VirtualBox is a dedicated key that returns the ownership of peripheral devices (Keyboard & Mouse) to the host operating system. You might be wondering about the Host Key. You just need to press a combination of Host key and C on your keyboard (Host Key + C). In order to exit scaled mode in VirtualBox, you need to follow below mentioned steps. In this mode, you might be having trouble in getting back to the Window mode or you might want to change settings of your virtual machine without restarting your VitualBox software. While using VirtualBox for emulating another operating system on your OS, you may have unknowingly entered into full screen or scaled mode.
