When RealVNC Viewer and RealVNC Server are installed on the same device and a connection is made between them, you will see an infinite "hall of mirrors", similar to the image below.
To resolve this, close the RealVNC Viewer session window. If you are unable to close the window using your mouse, you can force it to close by pressing Ctrl + W, or Command + W on macOS, on your keyboard.
When starting a connection please ensure you are selecting a computer that is different to the one you are running RealVNC Viewer on.
To see how easy it is to get set up with RealVNC Server on another computer, click the Getting Started guide link for your platform below: