In fact, SingleFile implements several ways to save space. In practice, the most effective mechanism is shaking the CSS tree. It's amazing how much CSS is usel

In fact, SingleFile implements several ways to save space. In practice, the most effective mechanism is shaking the CSS tree. It's amazing how much CSS is useless in a page. It's especially annoying for SingleFile if it contains images... That's why SingleFile removes (almost) all unused rules, selectors and CSS properties by calculating the CSS cascade.