The preload link tag is used to instruct the browser to download and cache a specific resource as soon as possible, without blocking the page's load. This is especially useful for resources that are needed early in the page's lifecycle, but are discovered late due to the manner they are called (like fonts, scripts, stylesheets).
<link rel="preload" href="styles.css" as="style"><link rel="preload" href="webfont.woff2" as="font" type="font/woff2" crossorigin><link rel="preload" href="large-image.jpg" as="image"><link rel="preload" href="script.js" as="script">