SEO Affected by Sizes Attribute in Images

Question

If we set sizes="(max-width: 450px) 50vw") of the image but later we will expand this image to full width. Will google penalize us for it as we expanded the image to 100vw but told Google to download 50vw via sizes?

<img src="/images/ac10.jpg" srcset="/images1/ac10-m4.jpg 800w ,/images/ac10.jpg 1100w" sizes="(max-width: 450px) 250px,1100px">

I want to counter higher DPR devices via the sizes attribute. If we set sizes="(max-width: 450px) 100vw") then on iPhoneX (DPR=3), Google will download (375*3 or 1125px) wide image which is huge. But if we set sizes="(max-width: 450px) 50vw") and later stretch image to width:100% then it will download (1125/2 px) wide image which will dramatically improve load time.

I want to know if this is cheating in Google's eyes as we are tricking google to download a 50vw size image and later we are using it as a 100vw size image. Will it affect SEO?

Answer 1

I wouldn't worry about it at all.

The biggest red flag for Google is if you're checking the User-agent and delivering different content specifically for Googlebot.

When it comes to cloaking Google is looking for deceitfulness. What you're doing doesn't sound deceitful, it sounds more like a progressive enhancement if anything.

If you're using Javascript to switch out the images, then Google probably is picking it up anyway, which should be fine.