A slow-loading website frustrates visitors and affects search rankings. If pages take too long to appear, people leave, and search engines notice. One major cause? Render-blocking resources: CSS and JavaScript files that delay content from displaying. Removing them helps your site load faster, improves user experience, and boosts performance in tools like Google PageSpeed Insights.
In this guide, you’ll learn what these files are, how to identify them, and the best ways to eliminate them. Whether you prefer quick plugin fixes or manual optimizations, we’ll cover both so you can improve speed without unnecessary hassle.
Table of Contents
- What Are Render-Blocking Resources?
- WP Rocket: The Easiest Way to Eliminate Render-Blocking Resources
- Autoptimize: The Best Free Alternative
- Manual Optimization Techniques for Advanced Users
- How to Identify Render-Blocking Resources
- Additional Performance Optimization Tips
What Are Render-Blocking Resources?
When you visit a webpage, your browser follows a sequence: it reads the HTML, fetches linked resources like stylesheets and scripts, and then renders the page for you to see. But sometimes, specific files, especially CSS and JavaScript, interrupt this process, forcing the browser to pause rendering until they are fully loaded. These are called render-blocking resources.
Browsers prioritize content in a way that ensures a smooth user experience. However, if they encounter CSS or JavaScript files at the top of the document, they must fully load and process them before rendering the page. This can cause unnecessary delays, especially when these files are not essential for displaying above-the-fold content (the portion of the page visible without scrolling).
Google measures website performance using Core Web Vitals, which include:
- Largest Contentful Paint (LCP): Measures how long it takes for the main content to load.
- First Contentful Paint (FCP): Tracks when the first visible content appears.
- Total Blocking Time (TBT): Evaluates delays caused by long-running scripts.
When your site has too many render-blocking resources, these metrics suffer, leading to lower rankings on Google and a poor user experience.
There are two primary approaches to eliminate render-blocking resources:
- Using Plugins: The most straightforward way, ideal for non-technical users.
- Manual Optimization: Offers more control, best for advanced users.
We’ll cover both so you can choose what works best for your site.
Using Plugins to Eliminate Render-Blocking Resources
If you want a quick and effective solution, plugins can handle JavaScript deferral, CSS optimization, and caching without requiring manual code changes. Here are the best options:
1. WP Rocket: The Easiest Way to Eliminate Render-Blocking Resources
WP Rocket is a premium caching plugin with built-in features to defer JavaScript, optimize CSS delivery, and improve page load speed. Unlike many caching tools, it doesn’t require complex setup. Just install, activate, and apply a few key settings. Here’s how to use it:
1. Install and activate WP Rocket on your WordPress site.
2. Go to Settings > WP Rocket > File Optimization.
3. Enable the following settings under CSS Files:
- Minify CSS files
- Optimize CSS delivery (eliminates render-blocking CSS)
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- Minify JavaScript files
- Load JavaScript deferred (removes JavaScript render-blocking)
- Delay JavaScript execution (prevents unnecessary scripts from running immediately)
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4. Click Save Changes and clear your cache.
WP Rocket automatically removes render-blocking resources while also handling caching, minification, and lazy loading. This is the best choice if you want a simple, one-click solution.
2. Autoptimize: The Best Free Alternative
If you’re looking for a free alternative, Autoptimize offers similar results. It aggregates, minifies, and defers scripts, helping to eliminate render-blocking resources and improve page speed.
1. Install and activate Autoptimize from the WordPress plugin repository.
2. Go to Settings > Autoptimize.
3. Enable these JavaScript Options:
- Optimize JavaScript Code
- Do not aggregate but defer?
- Also defer inline JS?
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Enable these CSS Options:
- Optimize CSS Code
- Eliminate render-blocking CSS?
4. Save changes and clear the cache.
For better results, pair Autoptimize with a free page caching plugin like Cache Enabler. This combination ensures both faster script execution and improved overall site speed.
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Manual Optimization Techniques for Advanced Users
If you prefer a hands-on approach or want more control over how your website loads resources, manual optimization offers a way to fine-tune your site’s performance. While plugins handle much of this work automatically, manually implementing these techniques can provide even greater flexibility and efficiency.
1. Defer and Async JavaScript Execution
JavaScript files can delay rendering when they load before the rest of the page content. By deferring or asynchronously loading scripts, you can improve page speed without affecting essential functionality.
Scripts should only load when needed. Adding defer or async attributes ensures they don’t block rendering:
- Use defer for scripts that must run in order after the page has fully loaded.
- Use async for scripts that can load independently without affecting others.
To apply these attributes, update script tags in your header or footer files (header.php or footer.php):
If scripts are enqueued dynamically by plugins or themes, check for settings that allow deferred loading.
2. Inlining Critical CSS for Above-the-Fold Content
To speed up rendering, browsers need immediate access to styles affecting the visible portion of the page (above-the-fold content). Inlining critical CSS allows the browser to load essential styles without waiting for an external file.
Here is how to generate critical CSS:
1. Use a tool like PurgeCSS or Penthouse to extract critical CSS.
2. Copy the generated critical CSS and paste it directly into your HTML section.
3. Load the remaining CSS asynchronously to prevent blocking:
This technique removes render-blocking CSS while ensuring the page loads with proper styling.
3. Removing Unused CSS and JavaScript
Many WordPress themes and plugins load extra CSS and JavaScript that aren’t required on every page. Removing these unnecessary files can significantly improve performance.
Find unused CSS and JavaScript:
1. Open Chrome DevTools in Google Chrome (Ctrl + Shift + I or Cmd + Option + I on Mac).
2. Navigate to More tools > Coverage.
3. Click Reload and check the list of loaded CSS and JavaScript files.
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If unused scripts are coming from themes or plugins, you can disable them selectively without modifying code.
You can use:
- Asset CleanUp to unload specific styles and scripts that aren’t needed.
- Perfmatters to disable CSS/JS files per page and remove bloat from WordPress.
4. Minify and Combine CSS & JavaScript
Minifying CSS and JavaScript removes unnecessary characters like whitespace and comments, reducing file size. Combining multiple files into one reduces HTTP requests, speeding up loading.
Here is how to do manual minification:
- Use online tools like CSS Minifier and JS Minifier to compress your files.
- Replace your original styles.css and script.js files with the minified versions.
For manual combination, merge multiple CSS files into one style.css file and multiple JavaScript files into one script.js file.
5. Optimizing Font Loading (Host Google Fonts Locally)
Fonts from Google Fonts often block rendering because they load from an external server. Hosting them locally can eliminate render-blocking.
Here is how to self-host Google Fonts:
1. Download your Google Fonts from Google Webfonts Helper.
2. Upload them to your WordPress theme’s /fonts/ folder.
3. Add the following CSS in your theme’s style.css file to load them:
@font-face {
font-family: 'CustomFont';
src: url("https://www.wpzoom.com/blog/eliminate-render-blocking-resources-wordpress/fonts/CustomFont.woff2") format('woff2'),
url('fonts/CustomFont.woff') format('woff');
font-weight: normal;
font-style: normal;
}4. Remove the Google Fonts tag from your theme’s header.php file.
Preloading fonts can further improve speed:
6. Reducing HTTP Requests with Preloading & Prefetching
Browsers often wait until needed to fetch specific files. Using preload and prefetch helps prioritize critical assets.
Preloading tells the browser to download critical files earlier, improving LCP. Here is how to preload essential resources:
Use preload for:
- Fonts
- Hero images
- Core JavaScript files
Prefetching tells the browser to prepare external assets for future use, reducing delays. Here is how to prefetch external resources:
Use prefetch for:
- Third-party scripts (Google Analytics, Facebook Pixel)
- CDN-hosted assets
How to Identify Render-Blocking Resources
Before eliminating render-blocking resources in WordPress, you need to identify which files are slowing down your site. There are several free tools that make this easy.
1. Using Google PageSpeed Insights
Google’s PageSpeed Insights (PSI) is the most accessible way to find render-blocking CSS and JavaScript. Here’s how to use it:
1. Visit PageSpeed Insights.
2. Enter your website URL and click Analyze.
3. Scroll to the Diagnostics section and look for “Eliminate render-blocking resources.”
4. Click the dropdown to view a list of blocking CSS and JavaScript files.
Each file listed contributes to slower loading times. If you remove or optimize these files, Google will also provide estimated time savings.
2. Running a Lighthouse Audit
Lighthouse is built into Chrome Developer Tools and provides a detailed breakdown of performance issues.
To run a Lighthouse audit:
1. Open Google Chrome and visit your website.
2. Right-click the page and select Inspect to open Developer Tools.
3. Navigate to the Lighthouse tab.
4. Tick the Performance category and click Analyze page load.
5. Look for render-blocking warnings in the diagnostics section.
Lighthouse will highlight which scripts and stylesheets are causing delays and suggest fixes.
3. Checking GTmetrix for Waterfall Charts
GTmetrix offers a visual representation of how files load on your site.
Steps to analyze render-blocking resources in GTmetrix:
1. Go to GTmetrix and enter your URL.
2. Click Test Now and wait for results.
3. Navigate to the Waterfall tab.
4. Look for longer bars in the CSS and JS rows; these indicate delays.
GTmetrix helps pinpoint exactly which resources are blocking rendering, making optimizing it easier.
4. Understanding How WordPress Themes & Plugins Contribute to Render-Blocking
Not all render-blocking issues come from core files. WordPress themes and plugins often introduce unnecessary scripts and styles.
- Some themes load multiple CSS files even when they aren’t needed.
- Certain plugins add JavaScript that blocks rendering, even if it’s not required immediately.
- Heavy page builders (like Elementor or Divi) often introduce extra scripts that slow down loading.
To identify problematic plugins and themes:
- Disable plugins individually and retest your site speed using PSI or GTmetrix.
- Switch to a lightweight theme (such as WPZOOM’s speed-optimized themes) and compare load times.
- Use a plugin like Asset CleanUp to disable unnecessary scripts on specific pages.
Additional Performance Optimization Tips
Eliminating render-blocking resources is just one part of WordPress speed optimization. To further enhance page load speed and Core Web Vitals, consider these additional performance techniques.
- Enable browser caching: Store static assets locally to reduce load times on repeat visits.
- Choose a lightweight theme: Avoid bloated designs that slow down performance.
- Reduce HTTP requests: Minimize scripts, combine CSS/JS files, and limit third-party resources.
- Enable lazy loading: Load images and videos only when needed to improve LCP.
- Use a CDN: Distribute content across multiple servers for faster global access.
- Optimize your database: Remove unnecessary data to keep WordPress running smoothly.
- Enable GZIP compression: Compress files before sending them to browsers to reduce file size.
For a complete guide to speeding up your WordPress site, check out our detailed optimization article: How to Speed Up Your WordPress Website.
A Faster WordPress Experience Starts with the Right Theme
Speed matters. Optimizing CSS and JavaScript helps, but your theme also plays a role. A well-built, lightweight theme reduces load times and works smoothly with caching and performance plugins. WPZOOM themes prioritize clean code and fast loading without extra complexity.
If you’re looking for a theme that balances design and performance, explore options that keep your site running efficiently. A few small changes can make a big difference in how visitors experience your website.
