Async CSS w/ link[rel=preload] This is a test page that references a slow-loading stylesheet using the new standard link[rel=preload]. That markup looks like this: <link rel="preload" href="slow.css.php" as="style" onload="this.rel='stylesheet'"> In supporting browsers (such as Chrome Canary at time of writing), this markup will cause the browser to fetch the CSS file in an asynchronous, non-rende