Font Awesome icons not working in OSX Safari

Question

My font-awesome icons are working fine in Firefox and Chrome, but in Safari I just see blank space for some of them but not others. Screenshot:

Answer 1

In my case I had the wrong font family for brand icons.

My old CSS:

font-family: "FontAwesome";

My new (working) CSS:

font-family: "Font Awesome 5 Brands";
font-weight: 900;

This should help anyone who is using old code & has issues displaying brand icons (Twitter, Facebook etc)