How To Defer Parsing Of JavaScript In WordPress

The speed of your website is an essential performance measure of how well it loads. The time a browser takes to run a website is page speed. Faster load times ensure that your website loads the largest number of visitors. In search engine results, page speed also partially defines your website's rank. Acceleration of a WordPress website is therefore often top of the wish list of a site owner. In this article, we will discuss defer parsing of Javascript in WordPress during loading of the web page, which is an essential way to eliminate unnecessary load from your website. Also, Premium WordPress themes are available on VWthemes.

How To Defer Parsing Of JavaScript In WordPress?

Let's take a look at how a web browser renders a page to better comprehend the approach of postponing JavaScript parsing. When your browser submits a request to your web server, the server returns a page in the form of an HTML document, which your browser downloads. Text, code that renders various DOM elements, and resources such as pictures, stylesheets, and scripts are all included in this HTML document.

This HTML markup is read line by line by the browser. In addition, all of the resources on the website must be downloaded. By default, the browser downloads these resources in the order in which they appear in the document. Once a resource has been downloaded, the rendering of the web page resumes.

Large resources affect loading time on a page. As pictures form a substantial part of the page size, optimizing images for your WordPress site is recommended. You must identify the scripts needed to render your page correctly for JavaScript files. To speed up your web page, you can defer downloading non-essential scripts. Check out WordPress templates on our website today and avail them at a discounted price.

How To Know Which Scripts To Defer?

No scripts may be required for loading a page for a relatively small website that uses minimum JavaScript in wordpress. However, a thorough analysis of all the scripts on your site may reveal the scripts necessary for page loading if you manage a more complicated web page defer parsing of javascript in WordPress.

One way to do the analysis is to remove scripts one at a time and check if there are errors during page loading from the JavaScript console. This process, however, requires considerable JavaScript and web technology knowledge.

A speed test tool such as GTmetrix is an easier method for evaluating which scripts are critical for your page load. Enter your site's URL and wait until the tool evaluates it. Go to the PageSpeed tab in the results page, and extend the section called "Defer Javascript parsing in WordPress.

Attributes Async vs. Defer

There are two methods in place a script does not interfere with a web page.

First, the script tag can be filled with an async attribute. This says that the browser loads the script asynchronously. In other words, as soon as the resource falls into the code, the browser begins to download the resources but then continues to parse the HTML during the download process.

Second, the script tag may contain a defer attribute. The browser should not download the resource until the page has been parsed. The browser downloads the list of deferred scripts previously found once the parsing and rendering are completed. When the resource is downloaded, the main difference is between the defer and async attributes. so you've got two scripts: A and B. B appears after A, B depends on A, but A is considerably greater than B. B is not the same. If async is used, B may be able to finish downloading before A is downloaded in its entirety. This results in an error, as in the absence of A B is performed. If defer is used, A and B will be downloaded sequentially at the end, which will not lead to a mistake.

You would find no difference between the use of async and delay if you only have few scripts in the rendering path. However, it can be a good idea to use defer to make sure that interdependencies are compliant with a complex web application. Along with this have a look at online shop store woocommerce for your website.

Ways Of Deffering Parsing Of Javascript In WordPress

  • Edit the.php File Functions

You know that it is not recommended to add scripts directly through the HTML markup if you have worked on WordPress development. Instead, you should apply for resources using built-in WordPress functions for defer parsing of javascript in WordPress.

So if you wish to add an async to any of your scripts or delay them. Use a computer. It may not be ideal for all to edit the source code through the functions.php file. You can simply use a plugin in your WordPress website if you are not technically knowledgeable to defer the parse of JavaScript. Async JavaScript is a free plugin for downloading and installing this task on your website. Select the JavaScript Enable option in the plugin's settings area to enable the feature.

You can also use the Autoptimize plugin created by the same author as Async Javascript to defer parsing your scripts.

In the settings page of the plugin, check the JavaScript Optimize code option, and delay and move your non-significant scripts to the footer. You can also list the scripts to which the async attribute should be added in the Extra tabs.


We discussed the importance of page speed and how JavaScript rendering and also defer parsing of javascript in WordPress works in this article. we examined two ways of achieving it in WordPress. You can either edit the functions.php file to add async, delay or use an Async JavaScript plugin to optimize your scripts. or defer attributes to your script tags.

VWTHEMES presenting you One of the best WordPress Theme Bundle, a Collection of 170+ WordPress Themes at just 99$.

Back to blog