etyetyFor loading CSS styles asynchronously, you should indicate it, as a preload stylesheet. Whenever you use rel="preload" alone, it won"t transform to stylesheet on page load and it will remain as preload, so to indicate it as stylesheet you should use another attribute such as as which indicate the type of element and in your case, it should be style. Then you need to tell the browser whenever the loading process got finished you need to consider this as a stylesheet, so you have to define another attribute like onload and then define its real relation. so you have to import it like this: NOTE: You can read more about it here in google developers. UPDATE Since preload is not supported in firefox until now (according to this), the only way to do it, is to declare it twice in the one rel tag or two separate tags.