Note: This article only applies to Windows and Mac computers running VNC Viewer.
Mac Viewer only: You need to disable "Displays have separate Spaces" in System Preferences, Mission Control. You also need to set UseLegacyFullScreenMode to True in VNC Viewer's global Preferences, via VNC Viewer -> Preferences in the menu bar.
VNC Viewer can be configured to fill all your local screens with the remote desktop.
To do so, first connect to VNC Server:
Next, click the Properties button on the VNC Viewer toolbar:
Select the Expert tab:
UseAllMonitors into the Filter, and set the Value to True:
Click OK. Click the Enter full screen button on the VNC Viewer toolbar:
VNC Viewer will now fill all your screens. To exit full screen mode, click the Exit full screen toolbar button again.