Introduction
## macOS
- Use `screencapture` (built-in): `screencapture -x output.png` for silent capture, `-i` for interactive selection - Capture specific window by PID: `screencapture -l$(osascript -e 'tell app "AppName" to id of window 1') out.png` - For retina displays, output is 2x resolution by default — add `-R x,y,w,h` to capture exact pixel region - iOS Simulator: `xcrun simctl io booted screenshot output.png` — faster and more reliable than screencapture
## Linux
- `gnome-screenshot` for GNOME, `spectacle` for KDE, `scrot` for minimal/headless - Headless X11: `xvfb-run scrot output.png` — creates virtual display for CI environments - Wayland sessions break X11 tools silently — use `grim` for Wayland, `slurp` for region selection
## Windows
- PowerShell built-in: `Add-Type -AssemblyName System.Windows.Forms; [System.Windows.Forms.Screen]::PrimaryScreen | ...` is verbose — prefer `nircmd savescreenshot` - `nircmd savescreenshot output.png` works from CLI without dependencies on most Windows versions - For programmatic capture, `python -m PIL.ImageGrab` works cross-platform but requires Pillow installed
## Web Pages
- Playwright: `npx playwright screenshot URL output.png --full-page` — handles JavaScript rendering and scrolling - Always wait for network idle: `--wait-for-timeout=5000` or page never finishes loading dynamic content - Full-page screenshots of long pages pixelate when viewed — split into viewport-sized chunks instead - Puppeteer equivalent: `page.screenshot({fullPage: true})` after `networkidle0`
## Format and Quality
- PNG for UI/text (lossless), JPEG for photos (smaller files) - JPEG quality 85-92 is optimal — below 80 shows artifacts on text, above 95 gains little - WebP offers 25-35% smaller files than JPEG at same quality — supported everywhere except older Safari
## Automation Patterns
- Add timestamps to filenames: `screenshot-$(date +%Y%m%d-%H%M%S).png` — prevents overwrites in batch jobs - For comparison testing, use identical viewport sizes — different resolutions create false diffs - CI screenshot artifacts: compress with `pngquant` or `jpegoptim` before upload — saves storage and transfer time