Now… tie this into an automated testing tool and gather results from a complete run-through of an app or site and you’ve got something you can actually use to improve your site’s performance.
It’s worth noting that there are static analysis tools for many task runners that can actually run queries against your HTML templates and remove unused styles automatically. I’ve used gulp-uncss
on a few projects and found it to work reasonably well (though you have to tune it for any JavaScript-related styles since it only consults your HTML to find matches).