Adding a Pinned Tab icon for Safari
With the release of Mac OS X 10.11, Safari finally got pinned tabs. While all other browsers use a site’s favicon for the pinned tab, Apple deemed that “not esthetically pleasing enough” and created a new type of icon for it, which they call a “mask-icon”. By default, they’ll use the first letter of your domain if you don’t have such an image. You need a black SVG image, a hover color and some time to do a tiny bit of coding.