User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0

Steps to reproduce:

Chrome is adding support for lazy loading images and iframes, as specified here: https://github.com/scott-little/lazyload/.

Actual results:

Firefox does not support this syntax, and I could not find an existing bug requesting it.

Expected results:

Firefox should also implement this. Currently, lazy-loading images not only requires using JavaScript, it also requires writing your HTML in such a way that your images will not be loaded at all with JavaScript disabled. Putting image lazy-loading in the browser's handling of the <img> tag makes it possible to provide this in a more robust way, lower down the web stack - you can confidently use the <img loading="lazy"> syntax and know that the fallback to eager loading will work in all browsers.

Bug report for the old "lazyload" attribute: https://bugzilla.mozilla.org/show_bug.cgi?id=947427

There isn't yet a reasonable spec for lazyload, but it does feel like a good addition to the web platform.

WHATWG Pull Request for "loading" attribute: https://github.com/whatwg/html/pull/3752

Migrating Webcompat whiteboard priorities to project flags. See bug 1547409.

See bug 1547409. Migrating whiteboard priority tags to program flags.

Starting with Chrome 76, you'll be able to use the new loading attribute to lazy-load resources without the need to write custom lazy-loading code or use a separate JavaScript library. — https://web.dev/native-lazy-loading