Latest update: July 24, 2024
When JavaScript halts the page from loading, it’s described as “render-blocking”. Essentially, if JavaScript obstructs the immediate visibility of content above the fold (the portion of your webpage visible without scrolling), it’s imperative to modify or remove it. Google highlights the significance of optimizing above-the-fold content loading to enhance user experience and page speed.
Above the fold refers to the portion of the webpage that is visible to users without scrolling, immediately upon loading. This visible area varies depending on the device being used, such as a smartphone, tablet, desktop computer, or any other device for viewing the webpage.
How to Іdentify Render Blocking JavaScripts?
It’s crucial to understand the content your page is loading. There are various methods to achieve this. You can utilize our request tool to gain insight into the challenges your page encounters. For specific files currently impeding rendering, the Google PageSpeed Insights tool is invaluable. It precisely identifies the files obstructing a particular page.
How to Remove Render Blocking JavaScripts?
JavaScript is often found, a prime example of which is jQuery, a JavaScript file used on a large portion of web pages. It is likely that your site uses it as well (you can check this with our tool). This JavaScript file tends to be quite bulky and could potentially be the largest file downloaded for rendering your page.
jQuery is a widely used JavaScript file, commonly employed for minor functionalities like image fade-ins or fade-outs. There’s typically no necessity to load jQuery before rendering your webpage, yet the majority of pages do so.
If the function involving jQuery occurs below the visible portion of the page (the fold), there’s no rationale for preloading it. By loading it prematurely, you contravene pagespeed guidelines and impose unnecessary waiting times on your users.
To rectify this issue, you need to adjust the placement of the jQuery call, typically found in the HTML of your webpage. Presently, most websites incorporate jQuery within the document’s header, as depicted below.
<head>
<meta name=description content="description here."/>
<title>title here</title>
<style>
styles here
</style>
<script src="jquery.js">
</script>
</head>The invocation of jQuery (a sizable file) necessitates downloading by the browser before any other page elements are displayed. This scenario is unfavorable, particularly egregious if the utilization of jQuery isn’t even required for the content visible above the fold, as depicted in the above image.
Practical Solutions and Tools
- Optimize Script Loading: Relocating jQuery and similar scripts to the bottom of your webpage or employing the async and defer attributes can prevent them from blocking the page’s render;
- Leverage Browser Caching: Storing frequently used JavaScript files in the user’s browser cache reduces the need for repeated downloads, speeding up subsequent visits;
- Use Google’s Recommendations: Google offers specific guidelines for deferring non-critical JavaScript, ensuring that critical content is prioritized in the loading process.
Example of Traditional vs. Optimized Script Loading
Before Optimization:
<head>
<meta name="description" content="description here."/>
<title>title here</title>
<style>styles here</style>
<script src="jquery.js"></script>
</head>After Optimization:
<body>
<!-- Content not requiring jQuery goes here -->
<script src="jquery.js" async></script>
<!-- Content requiring jQuery goes here -->
</body>The Role of Content Delivery Networks (CDNs) in Reducing Render-Blocking JavaScript
CDNs not only help in delivering content faster to users around the globe but also play a crucial role in optimizing JavaScript delivery. By hosting your JavaScript files on a CDN, you ensure they are retrieved from the nearest server to your user, reducing download times. Additionally, CDNs can minify and compress these files, further enhancing speed.
Implementing CDNs for JavaScript Delivery
Choosing a CDN that offers edge computing capabilities can allow for more intelligent scripting behaviors, such as device-specific optimizations and A/B testing, directly at the CDN level, without impacting your server’s performance.
By adopting these strategies and understanding the potential of CDNs in script delivery, developers can effectively mitigate the impact of render-blocking JavaScript, leading to faster, more responsive websites.
Conclusion
Efficiently handling render-blocking JavaScript is essential for improving webpage speed and user experience. Practical solutions like optimizing script loading and leveraging Content Delivery Networks (CDNs) can mitigate delays in page rendering. By implementing these strategies, developers can ensure faster, more responsive websites, ultimately enhancing user satisfaction and engagement.
