Download website icons with Favicon Downloader. Favicon Downloader can download all the different icons a website provides for various platforms including:
-mask-icon (mask-icon is an SVG image websites can provide for Safari tabs).
-Web app icons used in Android.
-Microsoft Pinned Site icons.
-Google TV icons.
You can type a website address in the app to view all the icons the website provides and optionally save the image files on your Mac.
You can purchase Favicon Downloader on the Mac App Store.