Sometimes I do not want an added drop shadow when I make a screenshot of a window. Luckily, you can disable it. You can chose if wou want to disable it only for the current screenshot, or for all future screenshots—and of course you can enable it again.
Disable it for the current screen shot
Hold Option while clicking, after you do Cmd + Shift + 4 + spacebar. The saved screenshot will not have an added drop shadow, all future screenshots will have it—except if you use Option again.
Disable it for all future screenshots
Execute the following command in your terminal, to disable the added drop shadow for all future screenshots:
defaults write com.apple.screencapture disable-shadow -bool TRUE
For the changes to take effect, you must reboot or restart the UIServer by executing the following:
You can undo the above, and re-enable added drop shadows, by executing the following:
defaults write com.apple.screencapture disable-shadow -bool FALSE
And again, you must reboot or restart the UIServer for the changes to take effect:
h/t to this question on Ask Different