Enabling Critical CSS is an indispensable point because speeding up website is not always synonymous with eliminating with your eyes closed. It is useful to simplify, it is okay to remove what is not needed and not part of the indispensable. However, this principle, taken to extremes, leads to one conclusion: nothingness.
Only a blank page can achieve the ideal result. Does this sound like an effective solution? No, that’s why you need to consider Critical CSS. What exactly is it about?
What is Critical CSS, definition
Cascading Style Sheets, Cascading Style Sheets, allow content to be styled with precise directions. That, however, can slow down the web page. Critical CSS is a methodology for optimizing page rendering time that allows loading only what is needed in the above-the-fold. That is, the most important and delicate section for improving the user experience.
With Critical CSS (the English term critical stands for important in this case) we prevent the browser from downloading all the style sheet files. But we suggest to analyze only those that are needed in the first stage of loading. Then operate on the rest at a later stage.
Must-read: tools for measuring site speed.
Why work on this front?
Implementing Critical CSS on your ecommerce, blog or website-especially those with a large amount of features related to style sheets-means facilitating the rendering of the first part of the web page at the moment when the user performs the request. We are at the most delicate stage, the one where you have to communicate to the user right away that you are there in the best possible way.
First Contentful Paint (FCP) is a critical metric that measures just that: the time it takes the browser to render the first part of the content.
The presence of Critical CSS can help substantially lower the values that weigh down web page loading. Especially when working from mobile with precarious connections. See how the loading job changes thanks to this timeline taken from Google’s web.dev.
Those involved in web performance know that you have to choose a compromise between functional needs, aesthetics, and good performance. We need websites that are fast, aligned with Core Web Vitals. But also beautiful to look at and capable of turning a visitor into a lead and then into a customer.
To achieve this goal, in real navigation and data measurement on Pagespeed Insight, we have several tools available in the toolbox. One of these is Critical CSS.
How Critical CSS is implemented.
There is a key principle: allow the section to follow only what it needs to load above the fold and leave everything else for later. This is done, in practical terms, by identifying the minimum CSS to render the content that loads immediately and inserting it into the HTML between the style tags in the head section. Here is an example.
Then with the function loadCSS(); we asynchronously load the CSS that is part of the non-decision area for our mission. Developing the heaviest CSS that is not necessary to the above the fold speeds up rendering times, and optimizes the presentation of the web page in the best way for the user experience. Which then falls under the various SEO ranking factors of an online resource.
Of course, creating all this for web pages is not easy, especially if you want to develop Critical CSS by hand. Fear not, there are valuable aids that come your way. How to enable a valuable contribution on your website in need of speed? There are different solutions.
Do you prefer to work like a true web craftsman? Don’t lose sight of the resource made available by github.com for discerning developers eager to get their hands dirty.
Online tools
There are several free tools available on the Internet for creating your own string of CSS to put in the above-the-fold to speed up the work of rendering, that is, rendering in terms of graphics. Which ones are the best? Is there a list to have at your fingertips? Here is my favorite toolbox:
Jonas Ohlsson Aden
With Jonassebastianohlsson.com the process is quite simple. You just have to choose how to extract the Critical CSS, whether by simply entering the URL or by copying and pasting the entire code.
Critical Path CSS Generator
Sitelocity.com/critical-path-css-generator is a Critical CSS generator similar to the previous one, only it eliminates the code solution: the ability to copy and paste the page URL remains.
At this point the tool scans the website and analyzes all the CSS files, returning the compressed version and the one that is to be placed in the above-the-fold as critical.
Pegasaas
Freemium service that connects to a broader and more articulated optimization universe. Similar to the previous tools, Pagasaas’ allows you to synthesize the CSS decisive to the rendering of the web page with just a few clicks. So you can insert it right where you need it to improve performance.
Plugins for WordPress
The truth is simple: there are extensions that allow you to enable Critical CSS on your WordPress website automatically, without any user effort. What are the names?
WP Rocket
A name that becomes a guarantee over the years. This plugin works wonders for those who want to optimize web pages and speed up loading. You can integrate everything from CDN to image compression. Of course, there is also the area for Critical CSS.
WP Rocket offers a simple and effective method. Enable Critical CSS, it is essential to minimize classic errors to eliminate render-blocking JavaScript and CSS recorded by Pagespeed Insight. Just click a checkmark and optimization is served.
Nitropack
Among the many plugins that allow you to optimize website performance, NitroPack allows you to perform a number of decisive functions. Such as, precisely, the inclusion of Critical CSS.
This is done in an automated way: the WordPress plugin detects and inserts the CSS needed to optimize above-the-fold content and optimizes it for each page. All this, however, without forgetting the other points of compression and reduction of both stylesheets and javascript.