Show HN: DropCSS – A simple, thorough and fast unused-CSS cleaner

DropCSS is an unused CSS cleaner; it takes your HTML and CSS as input and returns only the used CSS as output. It is recommended to also run your CSS through an optimizer like clean-css to group selectors, merge and remove redundant rules, purge unused keyframes, etc. Whether this is done before or after DropCSS is up to you, but since also minifies, it probably makes sense to run DropCSS first to avoid bouncing [and re-parsing] the output back and forth (optimize & minify -> drop) vs (optimize -> drop -> minify), though this will likely depend on your actual input; profiling is your friend.

Source: github.com