Critical Rendering Path

The critical rendering path is the sequence of steps a browser must take to process the HTML, CSS, and JavaScript files required to render the initial, above the fold view of a webpage. Optimizing this path involves minimizing the number and size of these "render-blocking" resources to allow the browser to paint content to the screen as quickly as possible. A long or bloated critical rendering path is a common cause of a slow First Contentful Paint (FCP).