We’ll modify our JavaScript to look like Listing 2, and we don’t need to change the HTML at all. ... The Fetch API is the modern successor of the earlier XMLHttpRequest().

If you do a basic Fetch, you can see the HTTP response that Google got from your page. When you do Fetch and Render , you get the response and get to see how your page looks in the specified browser.

Google To Add JavaScript Rendered Code In Fetch & Render Tool May 18, 2017 - 7:41 am 3 — by Barry Schwartz ...