CSS Delivery Optimization: How to Generate Critical CSS in WordPress?

How to Generate Critical CSS in WordPress

CSS delivery optimization is necessary to improve the core web vitals of the site. Using lots of themes and plugins on WordPress often adds up CSS files. These style.css files are however important for the appearance of the site, but sometimes influence the rendering of the page.

If you have tested your website with Google Page Speed Insights, you might have reported with “eliminate render-blocking resources” error. This warning comes when JS or CSS style sheets become too heavy to block the rendering of the content.  

To prevent this issue on your wordpress in the long run, generating and loading critical CSS can be helpful for the optimization of CSS delivery.

What is Critical CSS and Why it is Important for WordPress Performance?

What is Critical CSS and Why it is Important for WordPress Performance

Critical CSS is an optimization technique to extract the CSS for above-the-fold content for making the fast rendering of the content to the users. Above the fold denotes the content views once the page load, without scrolling down the page. The remaining CSS loads asynchronously.

Since critical CSS makes the rendering process a lot faster, here is how it can improve your WordPress performance:

  •         Improve first contentful paint (FCP)
  •         Improves first meaningful paid (FMP)
  •         Remove unused CSS
  •         Prioritize useful CSS

You see, critical CSS is key to optimizing the performance of wordpress.

So, the bigger your CSS files will be, the longer the time browser will take to process them. And, oftentimes, visitor requests get delayed with all these heavy CSS files by increasing the page load time.

Thus, it is crucial to generate critical CSS files and stop letting your core web vitals get affected. But you must be looking for how to generate critical CSS on your wordpress?

Generating critical CSS typically means optimizing CSS delivery. Read further to know.

Step by Step Process of Optimizing CSS Delivery 

Step by Step Process of Optimizing CSS Delivery

CSS handles your wordpress formatting and visual appearance. However, if the CSS files don’t deliver optimally, you can end up having a slow web page loading. Your visitors will see images, text, or content after a significant delay in the time.

That means, fastest WordPress themes would serve the page layout faster as they are optimized for speed.

But, in case, you don’t use premium themes on your wordpress, optimizing CSS delivery will be there to improve your WordPress site’s performance.

Here are three main steps to optimize CSS delivery for your WordPress site: 

Step 1 – Find and Generate the Critical CSS: Start with identifying the minimum CSS code you need to display the above-the-fold content.  Determining the right critical CSS for a page can be a daunting task because visitors use many different devices to browse websites such as desktop, tablet, and mobile.

To help you find out critical CSS, you can use tools provided WebDev Critical, CriticalCSS, and Penthouse.

Step 2 – Inline Critical CSS: To Inline critical CSS, add the critical CSS in the <head> of the HTML document to eliminate all the additional requests to fetch these styles.

Using inline CSS on critical page elements helps to speed up load time.

 Step 3 – Load the rest of the CSS asynchronously: Here you need to delay the non-critical CSS so it can be loaded when your visitors come to your web page content. It is also known as “deferred loading”. 

So, by following these three manual steps, you’ll successfully be able to optimize both your CSS delivery and your critical rendering path.

Moreover, you can also make this process easier with the help of a wordpress plugin and optimize wordpress CSS delivery right away.

How to Generate Critical CSS With a WordPress Plugin


W3speedster is an all-in-one WordPress plugin to help you deliver critical CSS and defer render-blocking resources including CSS and JavaScript.

This plugin will save your time with just a few clicks for the optimization of CSS. Thousands of online businesses have witnessed its great benefits in WordPress speed and performance optimization.

No matter what type of theme you use or how many issues you are facing on PageSpeed Insights, it is a complete plugin with varieties of automatic features such as minification of CSS/JS, image optimization, caching management, and much more.

We’ve put together the most essential functionalities so you can speed up your site precisely.


8 thoughts on “CSS Delivery Optimization: How to Generate Critical CSS in WordPress?

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