In Windows 10, when you use ALT + Tab to switch windows, the grid background is full black by default and the background windows and desktop icons are displayed, as shown in this image.
(Desktop icons shown in the background)
Hide Desktop Icons and Windows in Alt + Tab
Open Regedit.exe and go to:
Create a sub key and name it as AltTabViewHost
In the right-pane of AltTabViewHost key, create a REG_DWORD value named Wallpaper
Double-click Wallpaper set its data to 1
(Desktop icons and background windows hidden)
Make ALT + Tab Transparent
In the AltTabViewHost key, create DWORD value named Grid_backgroundPercent
Double-click the Grid_backgroundPercent value and set its data accordingly. (0 means fully transparent and 100 means full opaque. You may set something around 5 to 10.)
After setting it to 0, here is how it appears.
(Grid background 0%)
If the window titles are not clear, you may want to set the opacity to 10 or more.
(Grid background 10%)
Alternately, you can create a value named BackgroundDimmingLayer_percent, if you want to dim the background wallpaper (not the grid background) and set the opacity as required. Here I set the BackgroundDimmingLayer_percent to 40% (Decimal: 40), and here is how it looks.
(Grid Background 0% & Background dim at 40%, you can see the difference from previous image)
Exit the Registry Editor. There are plenty of other settings related to ALT +Tab, but most of them to be trivial.
Registry File for the Above Settings
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\MultitaskingView\AltTabViewHost] "Grid_backgroundPercent"=dword:00000000 "BackgroundDimmingLayer_percent"=dword:00000028 "wallpaper"=dword:00000001
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Ramesh Srinivasan founded Winhelponline.com back in 2005. He is passionate about Microsoft technologies and has a vast experience in the ITeS industry — delivering support for Microsoft's consumer products. He has been a Microsoft MVP [2003 to 2012] who contributes to various Windows support forums.