Before I can understand what EWWW IO does, I need to understand what happens to images in Wordpress.
I'm not a Web Developer but I know enough to get me through. Despite my knowledge I'm not quite sure how WordPress serves images.
Given that I know that Wordpress, your theme or your plugins automatically creates other copies of your image at other pixels dimensions respecting your aspect ratio.
My basic understanding is this.
In other words, I don't have a clue.
What I need to understand is why Browser Resizing takes place at all.