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How Can You Identify Render-Blocking Resources on Your Site?
To pinpoint which files are slowing down your page render, start with Google PageSpeed Insights. It highlights render-blocking CSS and JavaScript files under its performance recommendations. You’ll get a clear list of problematic resources that need attention.
Other helpful tools include:
- GTmetrix – Offers waterfall charts showing load order and timing.
- WebPageTest – Provides granular insights into resource loading and render delays.
Running these diagnostics is a crucial first step before making any code changes, ensuring you target the right files for optimization.
How can render blocking helps to Increase SEO performance?
When a user comes to a webpage, the web page speed at which the content is displayed significantly impacts their experience. Slow-loading web pages can lead to a poor first impression, increasing bounce rates. Reducing render-blocking resources ensures faster page load times, directly improving user experience and Core Web Vitals.
Faster-loading pages allow Google and other search engine bots to crawl and index your site more quickly, making it more visible on the Internet.
What Are Render-Blocking Resources, and Why Should You Remove Them?
Render-blocking resources are CSS and JavaScript files that prevent the browser from displaying visible content until they’re fully loaded and processed. This delays the initial rendering of your webpage, hurting both user experience and performance metrics like First Contentful Paint (FCP) and Largest Contentful Paint (LCP)—key indicators used by tools like Google PageSpeed Insights.
By manually eliminating or deferring these resources using PHP, you gain precise control over how your site loads—without relying on plugins that may introduce bloat or conflicts. The result? A faster, smoother experience for your visitors and a stronger SEO foundation.
How Do You Defer JavaScript Files Using PHP?
To defer JavaScript files, you can add a PHP snippet to your theme’s functions.php file. This snippet modifies the
async: Downloads and executes the script independently of HTML parsing.
defer: Downloads the script during HTML parsing but executes it afterward.
Here’s a simplified example using the script_loader_tag filter
function add_defer_attribute($tag, $handle) {
$scripts_to_defer = ['example-script', 'another-script'];
if (in_array($handle, $scripts_to_defer)) {
return str_replace('src', 'defer src', $tag);
}
return $tag;
}
add_filter('script_loader_tag', 'add_defer_attribute', 10, 2);
This method lets you selectively defer non-critical scripts while preserving essential functionality.
Can PHP Help With Render-Blocking CSS Files Too?
Yes—though the approach differs from JavaScript. The best strategy is to inline critical CSS: the minimal styles needed for above-the-fold content. You can extract this CSS and embed it directly into the of your HTML using PHP.
For the rest of your styles, use asynchronous loading techniques like the loadCSS pattern:
<link rel=”preload” href=”styles.css” as=”style” onload=”this.onload=null;this.rel=’stylesheet'”>
<noscript><link rel=”stylesheet” href=”styles.css”></noscript>
This ensures your page appears styled almost instantly, even before the full stylesheet finishes loading—dramatically improving perceived performance
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