Asynchronous loading

A type of page loading in which certain elements of the page load at the same time per directions in the code of the page. Normally, under synchronous loading, the browser will load the elements in order from the top to the bottom of the HTML of the page, but a script that’s loaded asynchronously will load while another does. Even if this cuts down on page load time, which has positive SEO benefits, developers should be careful of asynchronous loading while running A/B tests because it can cause a flicker while loading — the control version may load first and then flicker and ultimately show the variant.