Screenshot

macOS

• Use screencapture (built-in): screencapture -x output.png for silent capture, -i for interactive selection
• Capture specific window by PID: screencapture -l$(osascript -e 'tell app "AppName" to id of window 1') out.png
• For retina displays, output is 2x resolution by default — add -R x,y,w,h to capture exact pixel region
• iOS Simulator: xcrun simctl io booted screenshot output.png — faster and more reliable than screencapture

Linux

• gnome-screenshot for GNOME, spectacle for KDE, scrot for minimal/headless
• Headless X11: xvfb-run scrot output.png — creates virtual display for CI environments
• Wayland sessions break X11 tools silently — use grim for Wayland, slurp for region selection

Windows

• PowerShell built-in: Add-Type -AssemblyName System.Windows.Forms; [System.Windows.Forms.Screen]::PrimaryScreen | ... is verbose — prefer nircmd savescreenshot
• nircmd savescreenshot output.png works from CLI without dependencies on most Windows versions
• For programmatic capture, python -m PIL.ImageGrab works cross-platform but requires Pillow installed