CSS Debugging and Optimization: Minification with CSSO

Originally published at: https://www.sitepoint.com/css-debugging-and-optimization-minification-csso/

The following introduction to CSS minification tools is an extract from Tiffany’s upcoming book, CSS Master, 2nd Edition, which will be available shortly.

On your road to becoming a CSS master, you’ll need to know how to troubleshoot and optimize your CSS. How do you diagnose and fix rendering problems? How do you ensure that your CSS creates no performance lags for end users? And how do you ensure code quality?

Knowing which tools to use will help you ensure that your front end works well. In this article, we’ll discuss CSS minification.

Developer tools help you find and fix rendering issues, but what about efficiency? Are our file sizes as small as they can be? For that, we need minification tools.

Minification in the context of CSS simply means “removing excess characters.” Consider, for example, this block of code:

h1 {
    font: 16px / 1.5 'Helvetica Neue', arial, sans-serif;
    width: 80%;
    margin: 10px auto 0px;

That’s 98 bytes long, including line breaks and spaces. Let’s look at a minified example:

h1{font:16px/1.5 'Helvetica Neue',arial,sans-serif;width:80%;
    ➥margin:10px auto 0}

Now our CSS is only 80 bytes long—an 18% reduction. Fewer bytes, of course, means faster download times and data transfer savings for you and your users.

In this article, we’ll look at CSS Optimizer, or CSSO, a minification tool that runs on Node.js. To install CSSO, you’ll first have to install Node.js and npm. npm is installed as part of the Node.js installation process, so you’ll only need to install one package.

Using CSSO does require you to be comfortable using the command-line interface. Linux and macOS users can use the Terminal application (Applications > Terminal.app for macOS). If you’re using Windows, utilize the command prompt. Go to the Start or Windows menu and type cmd in the search box.

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