Hi @Jonathan0292,. Magento allows you OOTB to merge files but not to minify. There are several modules (free and paid) that works pretty well. Sometimes the minified and merged files can be a little problem on backend so you can minify and merge only the files for your store front and then use the regular calls to backend.
Apr 23, 2014 · Before doing anything, let's write our CSS minifier. Minifying CSS with PHP. Minifying consist of removing unnecessary whitespace and comments from the document. Thankfully, CSS syntax is not so complicated and we can minify it without breaking the code. In my minifier, I used just 2 steps: Remove the excess white space; Remove comments.
CSS Minifier Online CSS Minifier/Compressor. Free! Provides an API. Simple Quick and Fast. Written and hosted by Andrew Chilton (@andychilton) since 2009.
Minifying CSS means complete peace of mind while you perform development responsibilities. Fitting a minified CSS file during the production is the best way to go. It will surely help to increase site speed in long run and turn more organic traffic.