How to Optimize Your CSS for Performance? [GUIDE with EXAMPLES

Optimizing CSS is crucial to make a website fast loading. But it is not that much easy and straight that can be done without any technical knowledge. Make a fast loading website is a duty of both Developer and an SEO Person. It depend the organization where you are working which means as an SEO you must know how to optimize CSS Cascading Style Sheet to make a webpage fast loading and as a developer you should know obviously.

If we go to few years back then CSS was quite straight-forward and but with time like everything CSS is also improving. There are number of CSS frameworks available in the market that can make things dynamic on the website. With the advancement it become heavier in size that can affect the page load time directly if you do not work on it.

In this post we are going to share all the best practices that you should follow to minimize the loading time of a webpage that can be effected by the CSS using on the website for styling purpose.

Table of Contents

What Is CSS Cascading Style Sheet?

CSS, also known as Cascading Style Sheets, is a language used to design web pages after creating the markup structure with HTML. Some people believe CSS is a programming language, but it is not. It is, however, an essential part of website design and development.

How CSS affects Website Loading Speed Performance?

The easiest way to understand is with a simple example.

You are visiting a website.

As you open a URL it send a request to the server about the relevant files that you are trying to access. The server will send back the files to the browser. If the website is using a Minified CSS and HTML that can comparatively lower in sizes can load faster on your browser but on the other hand if the website files including the CSS files are not optimized for fast loading than it will irritate you and also will take a lot of time to load the complete page.

This is where the CSS optimization comes into play.

Minify CSS Files

Minifying your CSS removes unnecessary spaces, line breaks, comments, and reduces file size, which speeds up the loading time.

There are free online CSS Tools that can easily handle this kind of tasks. Our CSS Minified is one them. You can use our online free CSS Minified tool that will remove all the unnecessary spaces, line breaks, comments, etc. and optimize your CSS Files

Combine CSS Files

The more you have CSS files the more request will sent to your server by the browser on each HTTP request done by the user. Which mean the page speed will effect. What if you combine all the CSS files and make only one CSS file. It will ultimately lower the requests to the server and all the files will load once on the user browser.

This tip is very useful to make a website faster on mobile devices.

Remove Unused CSS (CSS Tree Shaking)

Scan your website to find the unused CSS files and remove them entirely to improve the performance of the website. There are tools like PurgeCSS that can find all the unused CSS.

Again this will save a lot of space and non-necessary HTTP requests to the server.

Use Critical CSS

Critical CSS are those CSS files that are important to load as the page loading. For example “Above The Fold” area is very important to load completely without any delay. Because it will make a good or a bad impression on the user.

If the “above the fold” area of your website is not loading on time that the user might think that the website is not running and maintaining by professionals and that might lose the trust also. It will also give a bad user-experience. So load the critical CSS files in the head section.

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Defer Non-Critical CSS

Just like using Critical CSS make Non-Critical CSS Defer. This will make the CSS load when necessary only and it will load once the other important files will load completely. You can set “CSS Defer” for content that are below the fold.

Avoid Inline CSS

I personally use inline CSS as a last option.

If you are aware about a term “SHORTHAND” in CSS, it can reduce the size of CSS a lot then writing a normal CSS code.

Example of Long Form and Shorthand CSS:

/* Long form */
margin-top: 10px;
margin-right: 10px;
margin-bottom: 10px;
margin-left: 10px;

/* Shorthand */
margin: 10px;

Use CSS Variables

As we mentioned earlier in this guide how CSS can make code dynamic. One example is using variables in CSS. Variables can reduce repetition of CSS code. If you are a coder you must know about variables.

Use Efficient Units

Instead of using em, rem, % or vw/vh using viewport can help you to improve the performance of a website. These units are more flexible and reduce the need for excessive media queries.

Lazy Load Fonts and Icons

It is really difficult to create a complete and fully functional website without using a font library or icons. One of the most famous and widely used font library is FontAwesome. These fonts and icons help us to make the job easy, fast and user-friendly but at the same time it is increasing and effecting the page load time of the website.

What you can do in such scenario is to use lazy loading and let the website use the system font until the external font is not fully loaded and ready to serve. Loading the system font can improve the page loading time and also give a better user-experience.

Optimize Media Queries

In today world no one can even imagine a website that is not responsive on all devices. Media Queries in CSS is an easy way to make a website mobile responsive. But using lot of media queries can affect the speed of the website.

The best way to use media queries is to group related styles together and apply media query. This will minimize the file size and also simplifies the maintenance of files. You need to work with feer files instead of lot of files.

Use CSS Grid & Flexbox, Not Floats

Using Floats in CSS is an old concept which is not very much efficient and it is also complex to maintain. Modern CSS layout method like Flexbox and Grid provide much more efficient, concise and performance-friendly layout capabilities. So if you are still using Floats switch to Grid or Flexbox today and improve your website loading time instantly.

Avoid Excessive Animations

Before developers need to use JavaScript to add animations but thankfully now we have animation available in CSS. But using animation excessively can affect the page loading time badly. .

How to Test CSS Performance for Free?

There are numbers of free and paid tool that can help you to check the CSS performance that need to be improved.

How to Fix CSS Performance Indirectly?