Jun 3, 2018

Asynchronous JavaScript files make for a better user experience.

When a person's browser loads a webpage, it loads the page's assets from top to bottom. When it hits a JavaScript file and wants to load it, if that JavaScript is not asynchronous, then the browser will stop loading everything else on the page until it loads that JavaScript file in its entirely.

If that JavaScript is asynchronous, then the browser will load it at the same time as it continues loading other elements on the page.