You want to take a screenshot of the active window? With the known CTRL + PRINT SCREEN you can only take a screenshot of the entire screen and then would have to to waste time copying the screenshot into a photo editing software and cutting out the desired window. Don’t waste your time! No need for the snipping tool, either.
Simply press ALT + PRINT SCREEN to take a screen copy of only the active window. You can then copy the image of the window by pressing CTRL + V into any open Office application, the Paint program, or after creating a correctly sized new empty image with CTRL + N into Photoshop and more.
For more shortcuts please also read: