Web pages often contain a large number of images, which contribute to data-usage, page-bloat and how fast a page can load. Many of these images are offscreen, requiring a user to scroll in order to view them.
Historically, to limit the impact offscreen images have on page load times, developers have needed to use a JavaScript library in order to defer fetching these images until a user scrolls near them.
These features are now coming natively to Chrome, and I hope to other browsers soon after.
Looks like it will be polyfillable, especially if we stick to the strategy of serving non-critical images via a very low-resolution file in ‘src’ and progressively enhancing as features become available.