Optimizing Javascript Assets for Page Speed in SEO

With the world going digital at an unbelievably rapid pace, there’s little wonder that website speed optimization and website performance improvement have become the buzzwords today. Site speed is indicative of how quickly your website is responding to web requests. Speeding up your website is crucial not just for your sake but for all the […]

With the world going digital at an unbelievably rapid pace, there’s little wonder that website speed optimization and website performance improvement have become the buzzwords today. Site speed is indicative of how quickly your website is responding to web requests. Speeding up your website is crucial not just for your sake but for all the potential and existing customers who visit your site as well.

The Significance of Website Speed Optimization

Site speed represents your website’s capability to quickly respond when a user clicks on an URL that redirects him or her to your website. According to Google PageSpeed standards, site speed is an important criterion for fast access to information, services, and products. Google makes use of site speed as one of the signals that are used by its algorithm for ranking web pages.

Users expect the websites they check out to load as quickly as possible. It has been proven that if you are not able to optimize page speed and load the content in a matter of seconds, they get frustrated and leave the site. Faster sites create satisfied users while visitors tend to spend less time on slow-responding sites.

Download speed impacts website performance.  Slow speed causes a web page to take longer to download and display its files and documents. High download speed, on the other hand, enables visitors to quickly access web pages and surf the Internet seamlessly. Here’s where website performance improvement plays an important role in making the users happy.

Key Steps to Optimize Page Speed

There are free online tools that help to test and optimize page speed, such as Pagespeed Insights, GT Metrix, Think with Google, Gift of Speed, and WebPage test. Website performance improvement can be achieved by using any of these tools.

By following certain powerful techniques, you can efficiently optimize page speed:

  • Minimizing HTTP requests is important: It has been proven that as high as 80% of the load time of a web page is spent on downloading various elements of the page such as stylesheets, scripts, and images. A separate HTTP request is made for each of these parts. Thus, the more number of on-page components, the longer the page rendering will take.
    • Figure out how many HTTP requests your site presently makes, use that as a benchmark, and minimize the requests.
  • Optimize your images: One of the primary requirements in website performance improvement is to compress the images while uploading the same on the server. Images play a vital role in e-commerce websites. These sites have a lot of images on their product pages that are instrumental in improving user engagement.
    • Images of large size take longer to load, thus affecting the overall page speed. You need to use a relevant compression technique and reduce the image size. Gzip helps to compress image size by about 70%
  • Reduce landing page redirects: Visitors are required to face additional wait time each time a page redirects to another. This is essential for the completion of the HTTP request-response cycle. Getting rid of unwanted redirects helps to optimize page speed.
    • Switching to responsive design helps you to avoid unnecessary redirects between the various versions of your website related to different devices such as desktop and mobile. Moreover, this ensures an excellent multi-device experience for visitors.
    • Choosing the right redirect type when you are required to use one is crucial. While a 301 redirect is good for permanent redirect, for device-specific URLs and short-term promotional pages, a temporary 302 redirect proves to be the best.
  • Make use of a content delivery network: When a site is hosted on a single server, all the users who visit the site will send requests to the same server. This leads to increased time for processing each request when there is heavy traffic on the site. Load time will be slowed down for all users. A content delivery network (CDN) helps to eliminate this issue.
    • A content delivery network, also known as a content distribution network, is a distributed system of networks of several servers that helps to distribute the work of content delivery. In this system, multiple copies of your site are stored at geographically diverse locations (data centers).
    • With a CDN, your visitors’ requests will be redirected to the nearest server. This reduces server load time considerably. Visitors are enabled to have more reliable and faster access to your website.
  • Minimize CSS and JavaScript files: Optimizing the code helps to increase the loading speed of your page dramatically. Minification of CSS, HTML, and JavaScript ensures that redundant data is eliminated from the resources that are delivered to your site visitors. This will facilitate overall website performance improvement. Online tools such as CSSNano and UglifyJS are recommended by Google in this regard.
    • CSSNano is useful for CSS minification if you run a small website and it doesn’t require frequent updates, but you wish to speed up the site.
    • UglifyJS, another online minifier, helps to get rid of the unnecessary data present in your code. Furthermore, it allows you to set up a process that minifies development files and also saves them to a specific production directory every time a new version is deployed by you.
  • Unused CSS must be removed: The role of CSS is beautifying your website. Unused-CSS.com reports that around 35% of CSS code proves to be unnecessary. Unnecessary CSS will naturally slow down website speed. The more unused CSS code, the more is the time taken by the browser to calculate the style for each node. It is essential to identify and remove unused CSS files to optimize page speed and achieve website performance improvement.
    • Before going in for minifying CSS files, check for the ones that you do not require and remove them promptly. Reducing resources is one of the simple but effective ways of website speed optimization.
    • Although manual deferring of uncritical CSS is possible, automating the process would be the better option. Online tools such as UnusedCSS, PurifyCSS, and PurgeCSS help in identifying and compressing the unused CSS files.
  • The use of web fonts must be reduced: It is well known that web fonts are a popular feature in modern website design. Although typography is a crucial aspect related to the accessibility, readability, and website design, more use of web fonts will negatively impact the speed of page rendering. Improper use of web fonts might even lead to blockage of website rendering, thus resulting in increased load time.
    • Web fonts lead to extra HTTP requests to external resources. Select only the necessary styles. Include only the character sets that have been used in the site. A list of web fonts format is given below that you may use according to the browser compatibility:
    • Choose WOFF for commonly used browsers
    • Use WOFF 2.0 for browsers that support it
    • Select TTF for old Android browsers
    • Use EOT to older browsers
  • Prefetching techniques must be used: Prefetching is a common technique that involves preloading or rendering resources before initiation by the users. This helps to save the time required to load the resources. This technique works effectively if you can anticipate user actions so that you can load some links or content in advance.
    • Modern browsers, with their ability to assume user behavior patterns, allow prefetching by default. There are three major types of prefetching:
    • DNS prefetching: Here, before the user performs an action, the domain name is resolved in advance. Examples are LinkedIn, Google Maps, and Google Analytics. Among other such domains, may be prefetched.
    • Link prefetching: This technique can be used on sites in which the user journey is stable. E-commerce websites in which users mostly navigate from the product page to the shopping cart page is an example.
    • Prerendering: This involves rendering an entire page itself or a few of the elements in advance.
  • Browser caching must be leveraged: The various elements of pages in the website you visit are commonly stored on your hard drive in temporary storage known as a cache. This enables the browser to load these pages without HTTP requests to the server, avoiding reloading the entire page. When once your page is loaded and the various components have been stored in users’ cache, just a few of the components need to be downloaded during future visits by the user.
    • Enabling caching helps returning visitors to save a significant amount of time, thus providing better user experience. Tools like YSlow are of use here. The approach to set up caching depends on whether the site runs with HTML or WordPress. Caching can be set up under general settings if you are using VPS or a dedicated server. Plugins such as W3 Total Cache and W3 Super Cache can be used for caching.
  • Render-blocking JavaScript must be removed: Browsers need to parse HTML and build a DOM tree for rendering a page. If the browser has to encounter a script while performing this process, it must stop and execute it, and then only continue. This makes the browser take longer for the rendering process. In the case of an external script, this delay is even more pronounced. By removing all the blocking JavaScript, you may avoid such delays.
    • You can make JavaScript non-render blocking.
    • You may defer third-party JavaScript libraries at least until after the fold.
    • Non-critical scripts may be made asynchronous; they may be deferred until after the first render.
    • Essential scripts required for rendering page content may be inlined. This helps to avoid extra network requests.
  • Implementation of lazy loading: Lazy loading is one effective technique that substantially reduces website load time. This website speed optimization involves loading only the requested component of a site while keeping the rest as it is. That will be loaded when the user requests for that specific component.
    • This improves user experience greatly and is particularly useful for pages that have a lot of content below the fold. Lazy loading allows loading the content that is within view first. The photos and images will be loaded after that. This relieves users from having to wait for accessing pages with images; the images will be loaded as they become visible. Lazy Load is a simple plugin that can be installed and activated easily.
  • Server response time must be reduced: The amount of time taken by domain name system (DNS) lookup plays a crucial role in the speed of loading a web page. The faster server response is now an essential factor. It has been determined that more than 50% of mobile visitors tend to abandon a page that wouldn’t load in three seconds.
    • To avoid slow routing, slow frameworks, slow libraries, central processing unit starvation, and slow application logic, high-quality website development is imperative.
    • Optimize for user experience.
    • Measure server response time as well as real user measurements.
  • Reduce excessive DOM size: Document object model (DOM) is an independent interface meant for HTML and XML documents. Due to inefficient coding practices and techniques, sometimes, unnecessary DOM trees are created. This hinders the speed performance of a website. A DOM tree with a complicated style, when it is too large, would impact factors such as speed, memory performance, and runtime.
    • The online tool Lighthouse can be used for checkṣing whether a website has an excessive DOM size problem. It is suggested to have a DOM tree that has less than a total of 1500 nodes, a maximum depth of 32 nodes, and doesn’t have a parent node with more than 60 child nodes.
    • Remove the unwanted DOM nodes. Consider also removing the nodes which are not displayed currently from the loaded document. Try to create these only after the user hits a button or scrolls down a page.


To be able to stand apart, modern businesses need to test their website speed and focus on the features and pages that call for action in this regard. Failing to optimize page speed will lead to slow-loading pages that frustrate your site visitors, and consequently result in a loss in conversion rates. Website speed optimization is the primary need for achieving website performance improvement, and subsequently, business growth.


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