A Layered Approach to Speculation Rules – Harry Roberts – Web Performance Consultant

I don’t want to go super in-depth about the Speculation Rules API in this post, but the key thing to know is that it provides two speculative loading types—prefetch and prerender—which ultimately have the following goals:

• prefetch pays the next page’s TTFB costs up-front and ahead of time;
• prerender pays the next page’s TTFB, FCP, and LCP up-front.

It’s going to be very helpful to keep those two truisms in mind—prefetch for paying down TTFB; prerender for LCP. This makes prefetch the lighter of the two and prerender the more resource-intensive.

Source: A Layered Approach to Speculation Rules – Harry Roberts – Web Performance Consultant