Understanding Render Blocking Resources in SEO: A 10-point guide

Through our SEO Agency Optimize 360
What is Render Blocking Resources in SEO?

The term "Render Blocking Resources" refers to elements that delay the display of a website.

When it comes to SEO, it is essential to optimise these resources to improve performance and user experience.

So let's take a look at the 10 key points you need to know on this subject.

Render Blocking Resources

1. What is render blocking?

Le render blocking occurs when certain resources (scripts, files CSS or others) block the rapid display of a web page. These resources prevent the browser from rendering the content in the first place, which increases the overall loading time.

2. The main resources concerned

The main culprits of the blocked render are the files JavaScript and CSS. These generally contain functions or layouts that need to be processed by the browser before the rest of the content is displayed.

a. JavaScript

JavaScript scripts are used to add interactive features to a website, such as animations, forms and drop-down menus. When these scripts are placed at the top of the page, they can generate render blockingbecause the browser has to run them first before continuing to load.

b. CSS

CSS style sheets determine the appearance of a site, including the design, colours and layout. Browsers must also process these files before displaying the content in full, which can cause render blocking if it is poorly optimised.

3. Why is this a problem for SEO?

Le web page loading time has a significant impact on the user experience and is an essential criterion for search engines such as Google. Slow loading times can lead to a drop in visitor satisfaction, and therefore a potential loss of traffic and ranking in search results.

4. How do you identify render blocking resources?

There are several tools and methods for detecting blocking resources on your site:

  • Audit Lighthouse available in Google Chrome's DevTools, provides a detailed report on performance problems, including render blocking.
  • Pagespeed Insights This free online tool from Google will also tell you what you need to optimise to reduce render blocking.
  • GTMetrix Another popular online tool for analysing your site's performance, with a section dedicated to render blocking.

5. Optimising JavaScript scripts

a. Deletion of unnecessary code

To reduce the impact of JavaScript on performance, remember to delete unused code and to slim your files by eliminating unnecessary spaces and comments.

b. Moving scripts to the bottom of the page

We recommend placing non-essential JS scripts at the bottom of the page to prevent them from blocking the rendering of content. In this way, the browser will already have loaded a large part of the site before executing these scripts.

c. Using the "defer" or "async" attribute

Add the "defer" or "async" attributes to the script tags, as appropriate, so that the browser can process the file while the page is loading without blocking the rendering:

  • Async : the script will be executed in parallel with loading, but may disrupt rendering if it is executed before loading is complete.
  • Defer : the browser only returns to script execution once the content has been fully loaded.

6. Optimising CSS files

a. Deleting unused styles

To optimise your CSS files, it is important to clean up your code by deleting superfluous or unused rules. Minimise your CSS files for additional performance gains.

b. Integrating critical styles into HTML code

Your critical styles are those needed to display the first part visible of your page (before the user scrolls). To speed up display, incorporate these styles directly into the code HTMLrather than calling them from an external file.

7. Use online resources to discover more optimisation options

There are numerous guides, articles and online forums that can help you learn more about optimising render blocking and further improve the performance of your website.

8. Combine files to reduce HTTP requests

Another aspect is to combine your CSS and JS files as much as possible to reduce the total number of HTTP requests, which will also have a positive impact on performance.

9. Operating a Content Delivery Network (CDN)

The CDN are used to speed up the delivery of files (images, scripts, fonts, etc.) to visitors by relying on a global network infrastructure. Using a CDN can significantly reduce your site's loading time.

10. Observe results with follow-up measurements

Finally, validate the effectiveness of your optimisations by regularly monitoring the key indicators relating to your site's performance, such as loading time or the rate of conversionto identify areas for improvement.

In short, optimising Render Blocking Resources is a crucial aspect of SEO for guaranteeing a satisfactory user experience and improving your site's search engine ranking. By putting into practice the advice presented in this 10-step guide, you are well on your way to optimising your rendering resources and boosting the overall performance of your website.

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