In reply to Bjarne.

I want to add that JS lazy loading still has performance advantages. The native lazy loading functionality isn't supported in all browsers but outside of that, it has the disadvantage of having a very large range for when it starts downloading images.

For instance, a typical lazy load plugin will fetch images in viewport immediately + 300 pixels maybe less outside of the viewport. However, native lazy load does the viewport + 1500 (most recent revision) which is substantially larger and is too eager. You will still see performance gains, at least for now by using the a JS library.