An old tip found on osxdaily.com. Copying it here since I’d like to have all the stuff I use when setting up a new mac machine in one place.
Screenshotting a window in macOS is simple: press Cmd-Shift-4, then Space and then select the window you’d like to make screenshot of. By default, macOS adds a window shadow on the screenshot which makes the resulting image bigger. I personally think this is unnecessary and prefer disabling the shadow on my screenshots. To do so, type these commands in your terminal of choice:
defaults write com.apple.screencapture disable-shadow -bool true
killall SystemUIServer