PurifyCSS
Remove unused CSS. Also works with single-page apps
...Remove unused CSS code from your stylesheet. PurifyCSS is meant to be installed via npm and built into your build process using tools like Grunt, Gulp or Webpack. However if you're using a different development stack or building your sites with a CMS like Wordpress, you can use the online tool to clean up your stylesheet. Especially if you are using CSS frameworks like Bootstrap or a multi-purpose Wordpress theme, chances are you are actually using less than 20% of the defined CSS rules.