Better HTTP/2 Prioritization for a Faster Web

The of the document comes after the head and contains the actual page content that is displayed in the browser window (though scripts and stylesheets are allowed to be in the body as well). Be patient when watching the animated progress because for the 19 seconds of blank screen it may feel like nothing is happening (even though it is):

Safari loads all resources in parallel, splitting the bandwidth between them based on how important Safari believes they are (with render-blocking resources like scripts and stylesheets being more important than images). In practice this is almost as good as the optimal loading case with the only difference being that the images load one at a time instead of in parallel:

Visually, the impact can be quite dramatic, even though they all take the same amount of time to technically load all of the content:

HTTP/2 prioritization is requested by the client (browser) and it is up to the server to decide what to do based on the request.

Source: blog.cloudflare.com