Preload CSS file not supported on Firefox and Safari Mac

Question

I added the attribute rel=\"preload\" to all css links like this :

Answer 1

I can't think of something more explanatory than the documentation itself. On the caniuse.com site there is this http://caniuse.com/#feat=link-rel-preload and if you follow that and go to the w3c specifications you find this. https://w3c.github.io/preload/ where is clearly stated that "This is a work in progress and may change without any notices." Maybe soon when this "Draft" will be refined, support will be added.