I developed a tool to be transparent on a window in Windows 10, using WINAPI, SetWindowLong, SetLayeredWindowAttributes and LWA_COLORKEY (C++). It can work on any window, however, it cannot work on web browsers. I found a same case,
Winapi - How to achieve equivalent of LWA_COLORKEY for MS Edge browser
SetLayeredWindowAttributes to make a window transparent is only working part of the time
and it can work on browsers not using hardware acceleration option. But, the actions on browsers are slow because of not using the hardware acceleration.
Is there another way to be transparent on a window? ( Can it work using Direct3D programing? and how?)