Lazy loading for images

[bzbarsky]

Request for Mozilla Position on an Emerging Web Specification

• Specification Title: Lazyloading of images/iframes below the fold
• Specification or proposal URL: Lazyload images whatwg/html#3752
• Caniuse.com URL (optional):
• Bugzilla URL (optional):
• Mozillians who can provide input (optional):

Other information

[annevk]

cc @smaug----

[smaug----]

Personally I do like the proposal, but it is still nowhere near ready. Especially it is unclear to me how 'auto' is handled and when 'auto' lazyloaded resources may or may not block top level page's load event to fire. (unless I'm missing something...)

[annevk]

Yeah, that is not defined. The intention is that it does not block it I learned yesterday. I raised that issue in a comment.

[dbaron]

It seems reasonable to me as well assuming it's specified sufficiently. Does worth prototyping seem like a reasonable summary?

[smaug----]

The affect to load event firing is very critical piece. Without that being defined, it isn't clear to me how the lazyload is supposed to work.

[smaug----]

Given that 'auto' is the default behavior in the latest PR, and 'auto' behavior is left to UA to decide, I consider that part rather harmful. I'd feel more comfortable if 'auto' was dropped altogether for now and the whole feature was always an opt-in.

[marcoscaceres]

That’s indeed an odd/harmful choice. Has that been raised as an issue? If whomever is proposing it not willing to change?

[digitarald]

Shipping in Chrome 67: https://web.dev/native-lazy-loading

Related, this is the caniuse URL: https://caniuse.com/#feat=loading-lazy-attr

[smaug----]

They will be shipping only parts of the lazyload proposal. Or that is what has been said on blink-dev at least. The default state for lazyload won't ship yet.

But note, there is no proper spec yet. There is a pr only.

[domenic]

The spec is as proper as it will get. Without a second implementer interested, per the WHATWG working mode, it will not be merged in to the HTML Living Standard. But the spec still exists, and is available for others to implement (or express interest in) at their leisure.

[smaug----]

The PR has unaddressed review comments.

[annevk]

Given the recent changes by @domfarolino and reduced scope (img only, no auto) I think this is worth prototyping.

[smaug----]

I agree, the recent spec pr is starting to have quite clearly defined behavior.