Going with your mouse pointer over a button in the taskbar, Windows shows you a preview of that window. Bu the preview is too small for example to understand something.
As usual many Windows settings cannot be changed from regular settings menu, but many of them you can change from the Registry, without downloading and using some third-party apps.
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Change the Size of the Taskbar Thumbnails
This will work on Windows 7, Windows 8 and Windows 10.
You will have to write in Run dialog box from Start Menu or start it simply with WIN + R key combination and type regedit.exe and hit enter, and then browse down through to the following registry key:
There right-click on the right-hand side and choose New -> 32-bit DWOR which should be named MinThumbSizePx then double click on it and give it value of 500 or less. This would be the pixels value.
Now you will have to logout and login again to check the results.
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