Skip to main content

CSS Performance Tips

In this tutorial, we will discuss some of the best practices to enhance the performance of your CSS code. These tips will help you write efficient, scalable, and maintainable CSS that leads to better user experience.

Understanding CSS Performance​

CSS performance generally refers to how quickly a browser can render your webpage. The faster a browser can parse and apply your CSS, the faster your webpage can load and become interactive. Here are some tips to improve the performance of your CSS.

1. Minimize HTTP Requests​

Each separate CSS file is a new HTTP request. The more requests your site makes, the slower it will load. Therefore, try to limit the number of CSS files on your site. You can achieve this by combining your CSS files.

/* Bad Practice */

<link rel="stylesheet" href="style1.css">
<link rel="stylesheet" href="style2.css">

/* Good Practice */

<link rel="stylesheet" href="combined.css">

2. Minify Your CSS​

Minifying your CSS means removing unnecessary characters (like spaces and line breaks) from your CSS code. Minifying can significantly reduce the size of your CSS files, thus speeding up load times.

/* Unminified CSS */

body {
  margin: 0;
  padding: 0;
  color: #333;
}

/* Minified CSS */

body{margin:0;padding:0;color:#333;}

3. Use Shorthand Properties​

CSS provides shorthand properties that allow you to set multiple related styles in a single line. This can make your CSS shorter and easier to read, which can also lead to smaller file sizes.

/* Without shorthand */

body {
  padding-top: 20px;
  padding-right: 30px;
  padding-bottom: 20px;
  padding-left: 30px;
}

/* With shorthand */

body {
  padding: 20px 30px;
}

4. Avoid Using @import​

Using @import in CSS can increase the time it takes for a webpage to load. This is because @import allows stylesheets to be loaded in parallel, which can slow down the page load.

/* Bad Practice */

@import url('more-styles.css');

/* Good Practice */

<link rel="stylesheet" href="more-styles.css">

5. Put CSS at the Top​

Placing your CSS at the top of your HTML document helps the page render progressively, improving the perceived performance. This is because browsers render HTML from top to bottom.

<!DOCTYPE html>
<html>
<head>
  <link rel="stylesheet" href="styles.css">
</head>
<body>
  <!-- Your content here -->
</body>
</html>

6. Use Efficient Selectors​

CSS selectors have different levels of specificity and efficiency. ID selectors are the most efficient, followed by class selectors, tag selectors, and universal selectors. Try to use efficient selectors to speed up rendering.

/* Less efficient */

div.navbar a {}

/* More efficient */

.navbar a {}

Remember, optimizing CSS performance is about writing CSS that's efficient for browsers to interpret and render, while also being easy for developers to manage and maintain. Always keep these two goals in mind as you write and optimize your CSS. Happy coding!