via make.wordpress.org => original post link
This post proposes adding the fetchpriority=”high” attribute to LCP images in WordPress core to enhance LCP performance. The proposal was created as a collaboration between members of the Core Performance Team.
Context
The fetchpriority attribute is a standard HTML attribute that can be used to indicate to the browser that a given resource should have a particular priority for when it should be considered for loading. Most commonly, using the attribute is recommended with a value of “high”, only on the most important image on a page.