What ARe REnder Blocking REsources?
Render-blocking resources in WordPress are typically JavaScript and CSS files that the browser must load before it can render the page content to the user. These resources are considered “blocking” because they must be fully downloaded, parsed, and executed before the browser can complete the process of displaying the page.
JavaScript as a Render-Blocking Resource
JavaScript files, especially when placed in the <head> of your document, are common culprits of render-blocking. The browser will not continue rendering the page until these scripts have been fully executed. This is because JavaScript can alter the content of the page, so the browser must process it to ensure it displays the correct version of the site.
CSS as a Render-Blocking Resource
CSS files are also render-blocking because they contain the styling rules needed for laying out the page. The browser needs to download and process all the styling information before it can correctly display the web page. If the CSS is complex or excessively large, it can significantly delay the page rendering.
Both types of files can affect the site’s performance, especially the perceived load time from the user’s perspective. Effective management of these resources—like optimizing their delivery and minimizing their size—can help in reducing their impact on your site’s load time.
How to Eliminate Rende Blocking Resources
Eliminating render-blocking resources is key to improving the load time and user experience of your WordPress site. Render-blocking resources are JavaScript and CSS files that the browser must load before it can render the page content to the viewer. Here’s how you can tackle these resources effectively:
1. Identify Render-Blocking Resources
Start by identifying which resources are render-blocking. Tools like Google PageSpeed Insights will point out these resources in its report. Look for suggestions about eliminating render-blocking JavaScript and CSS in above-the-fold content.
2. Optimize CSS Delivery
- Minimize CSS: Reduce the size of CSS files using tools or plugins that minify and combine CSS files. This reduces the number of files the browser needs to load.
- Inline Critical CSS: Identify and inline critical CSS. These are the styles needed for above-the-fold content. Tools like Critical Path CSS Generator can help you automatically generate and inline the critical CSS.
- Load Non-Critical CSS Asynchronously: For CSS not critical to initial page rendering, use the
rel="preload"attribute to load it asynchronously. This tells the browser to start downloading the file as soon as possible without blocking render. After preloading, you can use JavaScript to change it to a stylesheet when needed or rely on a plugin that handles this automatically.
3. Optimize JavaScript Loading
- Minimize JavaScript: Just like CSS, minimizing JavaScript files reduces their load time. Use plugins that can automatically minify and combine JavaScript files.
- Defer JavaScript: To defer parsing of non-critical JavaScript, add the
deferattribute to the script tags. This ensures scripts are executed only after the HTML is fully parsed. - Asynchronous Loading: Use the
asyncattribute for scripts that don’t depend on other scripts. This loads the script without blocking the DOM construction. - Remove Unnecessary Scripts: Audit your site for any scripts that are not essential and remove them. This might include tracking scripts, plugins, or any third-party scripts that aren’t vital.
4. Utilize a WordPress Optimization Plugin
Several WordPress plugins can automate the process of optimizing CSS and JavaScript. Here are a few:
- WP Rocket: This premium plugin offers features to automatically defer JavaScript, inline critical CSS, and asynchronously load CSS.
- Autoptimize: A free plugin that can aggregate, minify, and cache scripts and styles; it injects CSS in the page head by default but can also inline critical CSS and defer aggregated full CSS.
- Async JavaScript: This plugin gives you full control over which scripts to add an
asyncordeferattribute to.
5. Use a Content Delivery Network (CDN)
A CDN can help by caching your site’s static resources on a network of servers worldwide, which helps reduce the time it takes to deliver CSS and JavaScript files to the browser.
6. Testing and Validation
After making these changes, use PageSpeed Insights or similar tools to test your site again. This will help you understand the impact of your changes and whether further optimization is needed.
Eliminating render-blocking resources can significantly improve the loading time of your pages, especially on mobile devices where speed is crucial for user engagement and SEO. By implementing these strategies, you can ensure a smoother and faster experience for your site visitors.