An open source tool called Iroh.js, currently in beta development, allows JavaScript developers to perform dynamic code analysis to see exactly how their code behaves at execution.

Google explained that not all sites need to use dynamic rendering, that it is designed for pages where “content that changes rapidly, or content that uses JavaScript features that aren’t ...

In short, dynamic rendering is Google's way of helping you get your JavaScript sites indexed by Google. Google's John Mueller began explaining it a the 21 minute mark into the video.