On Google’s podcast, Martin Splitt explains how default lazy loading can delay LCP, why some libraries hinder indexing, and ...

Lazy-loading The lazy-loading HTML attribute tells a browser to either wait before downloading an image or to download it right away. There is no JavaScript need to accomplish this.

Mozilla has added support for lazy loading of images and iframes in the latest Nightly build of Firefox. It's disabled by default but enabling it to try out is simple enough, here's how to do it.