Thank you for hunting this!
emoji.css is different than other emoji libraries for CSS because it doesn't load any images. It uses the native unicode characters available on the platformāis that bad? is that good? Depends.
On Linux, you will get black and white emojis, on macOS and iOS you will see the Apple emojis, on Windows the Microsoft emojis etc.
It's like using the characters natively, but you can control them from the CSS, like an icon-font.
scrape-it