How to Eliminate Render Blocking Resources

TL;DR: Render Blocking is a vital part of website speed optimization. Even Google Page Insights also gives this solution to increase website speed. Let’s get into the know-how of render blocking, including what render-blocking resources are, how to eliminate them, and what is the impact of render-blocking on metrics.

What are Render-Blocking Resources?

Render-blocking resources are files that must load before anything on the website is displayed, such as render-blocking CSS and JavaScript. For a browser to render a page, it needs both the DOM (Document Object Model) and CSSOM (CSS Object Model).

Lighthouse for developers has identified two files, JavaScript and CSS, as render-blocking CSS resources. These files must be fully downloaded or parsed before the browser can render anything else on the page.

They are called render-blocking resources because they increase the load time of a website and delay or hinder the TTFP (Time to First Paint).

How to Find Render-Blocking Resources

There are several tools available that can help identify and resolve render-blocking resources. Two of the most recommended tools for this task are Google’s PageSpeed Insights (PSI) and WebPageTest. These tools are effective at pinpointing problem areas, such as render-blocking CSS, and assessing their impact on page performance.

Use Google’s PageSpeed Insights (PSI)

PSI provides a comprehensive audit that helps you identify render-blocking resources. In the “Opportunities” section, you can find render-blocking elements. Additionally, in the “Suggestions” section, you can check for potential improvements to enhance your site’s load times.

Use WebPageTest’s Waterfall Chart

WebPageTest is another useful tool that provides detailed insights through a waterfall chart. It highlights render-blocking resources with a small “X” and shows their impact on load times, as well as the browser that handles them.

What’s the Impact of Render-blocking on Metrics?

The primary impact of render-blocking resources on websites is an increase in load time, which can significantly affect user experience. Slow-loading pages can result in lost traffic and higher bounce rates.

Google’s PageSpeed Insights (PSI) scores a site’s performance based on five key factors:

First Contentful Paint (FCP)
Speed Index (SI)
Largest Contentful Paint (LCP)
Total Blocking Time (TBT)
Cumulative Layout Shift (CLS)

Render-blocking resources can have a significant impact on the following three metrics:

Largest Contentful Paint (LCP): A delay in LCP can occur when the largest visual element on the page takes longer to load, affecting the overall perceived load speed.
Total Blocking Time (TBT): Render-blocking resources increase TBT by preventing the browser from processing other critical tasks, such as user input or rendering other content.
First Contentful Paint (FCP): FCP is delayed when the browser cannot render content until render-blocking resources are fully loaded.

How to Eliminate Render-Blocking Resources without Plugins

Before eliminating render-blocking resources, it’s important to understand the concept of above-the-fold and below-the-fold content. Above-the-fold content refers to the first content or banner that appears on the page without scrolling, when a user opens the site.

To enhance the user experience, we need to minimize the load time of above-the-fold content so it loads instantly, and users don’t have to wait after opening the website. The goal is to make the website feel faster, even if below-the-fold content takes longer to load. This enhances your perceived performance.

Eliminating render-blocking resources is an essential step to reduce load time. The first step in this process is finding the critical CSS.

Critical CSS

Critical CSS refers to the render-blocking CSS involved in loading the above-the-fold content, which is directly visible when the website opens. The browser usually waits to render everything on the site until the entire CSS file downloads, which delays the First Contentful Paint (FCP) time.

One way to speed up this process is by inlining CSS into the HTML. By inlining CSS, the browser can render the page instantly before downloading the full stylesheet.

Benefits of Inlining Critical CSS

Increases the page load speed
Improves Core Web Vitals, especially LCP
Improves the perceived performance for the user

Additionally, critical CSS should be set up according to each device’s viewport, as users may view your site on different devices.

Eliminate Render-Blocking CSS

Inlining Critical CSS

Defer non-critical CSS
Split critical and non-critical CSS
Use as few CSS files as possible
Minify CSS files

Note: Ensure not to put the CSS in the header section (<head>) without implementing lazy loading.

A tool recommended for eliminating CSS is Sitelocity. You simply need to input the URL, but keep in mind that it is not completely reliable. It can, however, help experiment with CSS.

Eliminate Render-Blocking JavaScript

JavaScript is often the primary cause of slow page load times due to its resource-intensive nature. Heavy or large JavaScript files can significantly harm your site’s speed and take up considerable server space.

Use the Defer and Async Attributes

The defer and async attributes can be used to delay the execution of third-party scripts. These attributes make scripts non-blocking, minimizing their impact on the site load.

The key difference between the two attributes is that with defer, scripts execute in the order they appear, but they always run after the HTML document is fully parsed. With async, scripts execute independently, and the script that downloads first will execute first.

Split Codes

Code splitting allows you to break your JavaScript into more essential and less essential parts. By splitting the code, you can load the necessary, more useful scripts first and delay the less useful ones.

Tools like Webpack and Rollup are useful for breaking JavaScript bundles and splitting code into smaller parts. Code splitting optimizes speed and improves user engagement by allowing the browser to load only the necessary resources first.

How to Eliminate Render-Blocking Resources on WordPress

These techniques can be implemented on your WordPress site, as several plugins are available to handle the optimization of CSS and JS files. However, there are limited plugin options, so you may need to use multiple plugins to optimize all your CSS and JS code. This could lead to compatibility and code bloating issues.

The best approach is to find an all-in-one solution that prevents code bloating while seamlessly optimizing your code and files.

Finally, it’s important to focus on metrics and Core Web Vitals when optimizing your website’s speed. Tools and techniques are available to help, but they don’t capture every aspect of performance. It’s essential to apply these techniques thoughtfully, keeping your visitors’ needs and priorities in mind.

Faq’s

How to eliminate render blocking resources in WordPress without plugins?

By inlining critical CSS, deferring or async JavaScript, minifying CSS nd Java files, lazy loading images and media, you can eliminate render blocking on your website.

How do I check for render blocking resources?

There are some tools like Google PageSpeed Insights and WebPageTest, that provide website audits and highlight the render blocking CSS and JavaScripts.

What is a render blocking resource?

Render blocking resources are the files that hinder the downloading of website page content and components as they download first, making the page load slowly.

What is critical CSS and why is it important?

It is the minimum amount of CSS used in the loading of above the fold content of a website. It boosts the load speed of a website and enhances user experience.

What effect does render-blocking have on SEO?

It increases the website load time, which affects Core Web Vitals, which harms the chances of the website in rankings. As load speed is a vital factor for search engine rankings.

admin

August 14, 2025

Website Speed Optimization