A fitting image source should be available for all screen sizes

[rocc-o]

Hello, I get fitting image source problem as follows:
At a viewport of 320x427 the image was displayed 272 pixels wide, but the closest provided image has a width of 603 which is 55% off. The affected viewports are 300x169-340x453.

Strange though that in my source is specified media="(min-width: 568px) for srcset width 603w, while media="(max-width: 567px)" has the 320w and I believe is this one that Lint should consider for viewports 300x169-340x453. Am I missing something?

Here's my markup:

<picture class="promo__image">
	<source
		media="(max-width: 567px)"
		sizes="(min-width: 1740px) 630px, (min-width: 1040px) calc(37.94vw - 23px), 85vw"
		srcset="
			/assets/images/manifesto/webp/portrait/320.webp 320w,
			/assets/images/manifesto/webp/portrait/640.webp 640w
		"
		type="image/webp"
	>
	<source
		media="(min-width: 568px) and (max-width: 2560px)"
		sizes="(min-width: 1740px) 630px, (min-width: 1040px) calc(37.94vw - 23px), 85vw"
		srcset="
			/assets/images/manifesto/webp/landscape/603.webp 603w,
			/assets/images/manifesto/webp/landscape/1260.webp 1260w
		"
		type="image/webp"
	>
	<source
		media="(max-width: 567px)"
		sizes="(min-width: 1740px) 630px, (min-width: 1040px) calc(37.94vw - 23px), 85vw"
		srcset="
			/assets/images/manifesto/jpeg/portrait/320.jpg 320w,
			/assets/images/manifesto/jpeg/portrait/640.jpg 640w
		"
		type="image/jpeg"
	>
	<img
		sizes="(min-width: 1740px) 630px, (min-width: 1040px) calc(37.94vw - 23px), 85vw"
		srcset="
			/assets/images/manifesto/jpeg/landscape/603.jpg 603w,
			/assets/images/manifesto/jpeg/landscape/1260.jpg 1260w
		"
		src="/assets/images/manifesto/jpeg/landscape/1260.jpg"
		alt=""
		loading="lazy"
		width="1260"
		height="709"
	>
</picture> 

[ausi]

Can you please try if the error goes away if you remove the type="image/jpeg" from the last <source> element?

[rocc-o]

Yes! It's gone! But why? And also, is fine to leave it like that, without specifying type="image?

[ausi]

And also, is fine to leave it like that, without specifying type="image?

Yes, type="image/jpeg" in not needed because every browser supports that anyways.

But why?

Because the linter thinks that maybe some browser doesn’t support image/jpeg in which case they would fallback to the <img>.

[ausi]

I’d like to keep this issue open to remind me of adding a check for type="image/jpeg" and similar types.