How to Capture a Mac Window Without Its Drop Shadow

Take a window screenshot on Mac without the drop shadow, using the Option key for one capture or a Terminal defaults command to disable it permanently.

1. Switch to window capture mode. Press Command + Shift + 4. The pointer becomes a crosshair. Press the Space bar and the crosshair becomes a small camera. Move it over any window and that window highlights. Click and only that window is captured, cropped to its own edges.
2. Hold Option as you click. With the camera pointer over the window you want, hold Option and click. The window is captured with no shadow and no transparent margin around it. The file is smaller and the image edges sit exactly on the window edges.
3. Disable the shadow permanently. Open Terminal from Applications > Utilities. Type defaults write com.apple.screencapture disable-shadow -bool true and press Return. Then type killall SystemUIServer and press Return. Window captures from that point on arrive with no shadow, no modifier key required.
4. Reverse the change when you need it. Run defaults write com.apple.screencapture disable-shadow -bool false, or remove the key entirely with defaults delete com.apple.screencapture disable-shadow. Follow either one with killall SystemUIServer. The shadow returns on the next capture and the Option key behaves as it did before.
5. Check the result before you use it. Select the capture in Finder and press the Space bar. A shadowed window screenshot shows a soft grey halo on all four sides against the Quick Look background. A clean one stops at the window corners. Look at it before pasting it into anything.