Clears the junk out of your CSS by finding out which selectors are actually not used in your HTML.

By Peter Bengtsson, 2012-2013

With the onslaught of Twitter Bootstrap upon the world it's very tempting to just download their whole fat 80+Kb CSS and serve it up even though you're not using half of the HTML that it styles.

There's also the case of websites that have changed over time but without the CSS getting the same amount of love refactoring. Then it's very likely that you get CSS selectors that you're no longer or never using.

This tool can help you get started reducing all those selectors that you're not using.

No, that's a separate concern. This tool works independent of whitespace compression/optimization.

For example, if you have a build step or a runtime step that converts all your CSS files into one (concatenation) and trims away all the excess whitespace (compression) then the output CSS can still contain selectors that are never actually used.

If you have a script that creates DOM elements in some sort of window.onload event then mincss will not be able to know this because at the moment mincss is entirely static.

So what is a web developer to do? Simple, use /* no mincss */ like this for example:

.logged-in-info {
    /* no mincss */
color: pink;
}

That tells mincss to ignore the whole block and all its selectors.