How to Defer Parsing of JavaScript in WordPress ⚠️

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as someone who’s been working with WordPress for years I’ve always been a little hesitant about messing with JavaScript.

It seems like such a delicate dance and one wrong move could bring your entire site crashing down.

But recently I stumbled upon this amazing trick called deferring JavaScript parsing and it’s been a total game-changer.

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Deferring JavaScript: A Faster Smoother WordPress Experience




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Let’s face it everyone wants a website that loads lightning fast.

It’s not just about keeping visitors engaged; it’s also about those precious SEO rankings.

That’s why I’m so excited about deferring JavaScript.

It’s a simple tweak but it can make a huge difference in how quickly your WordPress site loads.

Think of it this way: your website is like a giant orchestra and each piece of content from images to text to JavaScript is a different instrument.

When your browser loads a page it tries to play all the instruments at once.

But with deferring JavaScript you tell the browser to hold off on the JavaScript “instruments” until everything else has loaded.

This means that your visitors see the main content of your page right away while the JavaScript loads and plays in the background.

The result? A much faster and smoother experience for your users and better performance scores to boot!

How to Defer JavaScript Parsing in WordPress: Two Simple Methods

Now you might be thinking “That sounds great but how do I actually defer JavaScript in WordPress?” Don’t worry; it’s not as complicated as you might think.

There are two main ways to do it:

1. The Easy Way: Using Jetpack Boost

If you’re not a coding wizard I highly recommend using a plugin like Jetpack Boost.

It’s like having a personal website performance guru at your fingertips and it makes deferring JavaScript ridiculously easy.

Just install the plugin and it will take care of everything for you.

No need to dig into theme files or write complex code.

You’ll find a setting in Jetpack Boost specifically for deferring JavaScript.

Just flip the switch and your site will automatically start loading faster.

2. The Manual Method: Editing Your functions.php File

For those who love tinkering under the hood there’s always the manual method.

This involves editing your theme’s functions.php file which can be a bit more daunting.

But if you’re comfortable with code it gives you more control over how you defer JavaScript.

Before you jump in I highly recommend taking a full backup of your website.

That way if anything goes wrong you can always restore it to its previous state.

Here’s how to edit your functions.php file:

  1. Access your Theme File Editor: Go to Appearance > Theme File Editor in your WordPress dashboard. If you’re using a block theme that supports Full Site Editing you may need to find a different way to edit this file.
  2. Locate functions.php: Select your active theme from the dropdown menu and you’ll see a list of files. Find the functions.php file.
  3. Add the Defer Script: Paste the following code at the end of the functions.php file:
function defer_parsing_of_js( $url ) {
    if ( FALSE === strpos( $url '.js' ) ) return $url;
    if ( strpos( $url 'jquery.js' ) ) return $url;
    return str_replace( ' src=' ' defer src=' $url );
}
add_filter( 'script_loader_tag' 'defer_parsing_of_js' 10 2 );
  1. Update the File: Click Update File at the bottom of the page.

This code will automatically defer all JavaScript files on your site except for jQuery scripts.

However it won’t work if you’re logged into your dashboard so be aware of that.

If you prefer editing the functions.php file through FTP:

  1. Connect to your server: Use an FTP client like FileZilla to connect to your website’s server. Remember always take a backup before making any changes!
  2. Locate functions.php: Navigate to the WordPress root folder (usually named www public_html or your site’s name) and go to wp-content/themes/your-theme-folder/functions.php.
  3. Edit the file: Right-click on functions.php and choose Edit to open it in your default text editor.
  4. Add the code: Paste the code snippet I shared earlier at the end of the file.
  5. Save the changes: Save the file.

The Benefits of Deferring JavaScript: Faster Loading Better UX

you’ve got your JavaScript deferring but what’s the big deal? Well it’s all about improving the user experience.

When JavaScript is deferred the browser can focus on loading the essential content like images text and headings first.

This results in:

  • Faster page load times: This is especially important in today’s fast-paced digital world where people expect instant gratification. No one wants to wait around for a website to load.
  • Improved Largest Contentful Paint (LCP) score: LCP is a key metric for Google’s Core Web Vitals and a faster LCP can lead to higher rankings in search results.
  • A better user experience overall: When your site loads quickly visitors are more likely to stay engaged explore your content and interact with your call to action.

Deferring JavaScript: Addressing Common Concerns

I know you might have some questions.

After all JavaScript is a crucial part of most websites.

Here are some common concerns and their answers:

Will deferring JavaScript break my website?

It’s possible but less likely if you use a plugin like Jetpack Boost.

Plugins are designed to be safe and easy to use so you can test the deferring feature and easily deactivate it if you encounter any issues.

However if you’re using the manual method make sure to test your website thoroughly after making any changes.

It’s also important to understand the code you’re adding and to defer only non-essential JavaScript.

What about render-blocking JavaScript?

Render-blocking JavaScript refers to any code that prevents your browser from rendering the rest of the page.

It’s a different beast than deferring JavaScript but it can be a major performance drain.

If you’re using a website performance analysis tool like PageSpeed Insights or GTMetrix you’ll often see recommendations to eliminate render-blocking JavaScript.

It’s best to do this if possible but if you need the functionality you can also defer it instead.

What about unused JavaScript?

Over time it’s easy to accumulate unused JavaScript on your site especially if you install and deactivate plugins or try out different services.

This code can impact your site’s performance and even pose a security risk.

To find unused JavaScript you can use a tool like GTMetrix which will highlight any scripts that aren’t being used.

You can then safely remove these scripts or defer them.

How much of an impact will deferring JavaScript have on my site’s performance?

It depends on how much JavaScript your site uses and how optimized your website is.

If you have a lot of JavaScript you’ll see a more noticeable improvement in page load times.

Even if you have a fast website already every bit of optimization helps!

Going Beyond Deferring JavaScript: Optimizing Your Website for Speed

Deferring JavaScript is a great first step towards a faster website but it’s just one piece of the puzzle.

Here are some other tips for optimizing your WordPress site:

  • Minimize image sizes: Use optimized images in formats like WebP or JPEG 2000 and ensure that your images are responsive.
  • Enable lazy loading: Lazy loading prevents images from loading until they’re visible in the user’s browser window.
  • Minify HTML CSS and JavaScript: Minification removes unnecessary characters from your code reducing file sizes and improving load times.
  • Use a CDN: A Content Delivery Network (CDN) distributes your website’s files across multiple servers allowing for faster loading times for users around the globe.
  • Cache your website: Caching stores copies of your website’s files so that they can be delivered faster to visitors.

Conclusion: Deferring JavaScript Is a Game-Changer

If you’re looking for a quick and easy way to improve your WordPress website’s performance deferring JavaScript is a must-try.

It’s simple it’s effective and it can make a world of difference in how your site feels to your visitors.

And remember there are other ways to optimize your website for speed.

Take some time to explore the different options and find what works best for you.

You’ll be surprised at how much you can improve your website’s performance with a little effort.

So go ahead give deferring JavaScript a try.

You’ll be glad you did!




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