[Support request] How do I load responsive featured Image?

Is there something unclear?

Hello David,
Thanks for your response.

Setting Medium doesn’t help. As I have different layout based on screen resolutions.

Current Settings

My requirement is

1. Mobile & Tablet: Serve Thumbnail size for screen resolution under 1024px.
2. Anything else: Serve Medium size for anything above 1024px.

In other words –

function Media_Attachment_Size( $max_width ) {
   if ( $max_width <= 1024 ) {
    // return 'Thumbnail' (Smallest one as per my settings )
    }
    // return 'Medium'
}

What I tried?

Using switcher doesn’t let me set conditional Media Attachment Size

Ref: Video

Thanks

In the mobile screen,

I selected Thumbnail and tested in mobile, it looks good, I want that. On desktop, it looks too small that is something I don’t like and a reason why I need to serve conditional featured image size.

Choosing “medium” works good at both but in mobile knowingly there is file size is bigger.
Thus, it cause issue in PageSpeed insight with message ‘Properly size images’.