Symptom
On a Windows 10 or Windows 11 device with a built-in display, when you connect an external monitor with a USB-C, DisplayPort, or HDMI connection, the wallpaper on the external monitor might not correctly fill the screen.
Cause
This problem might occur on Windows 10 or Windows 11 if the screen resolution of the built-in display differs from the screen resolution of the external display. When the screen resolution of the built-in display is smaller than the external, then the wallpaper on the external display might appear to be too small and doesn't fill the whole screen. When the screen resolution of the built-in display is larger than the external, then the wallpaper on the external display might appear to be too big and will be cut off on the right and bottom sides.
Resolution
You can resolve this issue by temporarily changing the screen resolution of the external display. To do this:
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Select Start > Settings > System > Display, and look at the section that shows your displays. Open your Display settings
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Select the external display.
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In the Display resolution row, select the dropdown and choose any screen resolution that differs from the display’s current resolution.
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Once the resolution changes, you will be asked if you would like to “Keep these display settings?” Select Revert. (The screen resolution will automatically revert if you take no action.)
