This site has been acquired by Toptal.com.
(Attention! API endpoint has changed)

CSS Minifier

Online CSS Minifier/Compressor. Free! Provides an API. Simple Quick and Fast.

Wget

# minifying some CSS
wget --post-data='input=p { color : red; }' --output-document=- https://www.toptal.com/developers/cssminifier/raw

# minifying a CSS file (e.g. style.css -> style.min.css)
wget --post-data="input=`cat style.css`" --output-document=style.min.css https://www.toptal.com/developers/cssminifier/raw

Click on the language of your choice to see an example: