Preload to optimize the loading of late-discovered resources. Normally large or hero images below the fold. By preloading a resource, you tell the browser to fetch it sooner than the browser would otherwise discover it before Native lazy or lazyloader JavaScript kicks in, or starts its own preload or decoding. The browser caches preloaded resources so they are available immediately when needed. Nothing is loaded or executed at preloading stage. <br>Just a friendly heads up: do not overuse this option, because not everything are critical, <a href=':url'>read more</a>.