Lazy loading for iframes

[zcorpan]

Request for Mozilla Position on an Emerging Web Specification

• Specification Title: Lazy loading for iframes
• Specification or proposal URL (if available): https://html.spec.whatwg.org/multipage/iframe-embed-object.html#attr-iframe-loading
• Explainer URL (if available): https://github.com/scott-little/lazyload
• Caniuse.com URL (optional): https://caniuse.com/loading-lazy-attr (images and iframes)
• Bugzilla URL (optional): https://bugzilla.mozilla.org/show_bug.cgi?id=1622090
• Mozillians who can provide input (optional): @hiikezoe @emilio

Other information

Also see #151

[zcorpan]

We support lazy-loaded images, and the feature makes sense for iframe for similar reasons. Initial page load is faster and more lightweight if out-of-view iframes are lazy-loaded. It's possible for sites to implement lazy-loading with JS but a declarative solution is easier to use and allows browsers to control when to load things.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1622090#c10 for an example of real-world impact.

Suggested position: positive.

[emilio]

I agree fwiw.

[martinthomson]

@zcorpan did you intend to add this to the dashboard?

[CanadaHonk]

This will soon be landed and most likely shipped, could we close this out?