How To Reduce Unused JavaScript?

Reduce unused JavaScript” is a crucial practice in optimizing websites and web applications to enhance performance and user experience.

So by the end of this article, we will know what this reduce unused Javascript means, why we need to reduce unused Javascript, how we can reduce it along with on how to check it.

What does reduce unused JavaScript mean?

“Reduce unused JavaScript” refers to the process of optimizing a website or web application by eliminating or minimizing the amount of JavaScript code that is not necessary for the current page or functionality.

Why do we need to Reduce Unused JavaScript?

Reducing unused JavaScript is essential for several reasons, primarily to optimize website performance and improve user experience.

Here are the key reasons why reducing unused JavaScript is important:

Faster Load Times

Unused JavaScript adds extra code that the user’s browser must download. This lengthens the time it takes for the page to load, especially for those with weaker devices or slower internet connections. User retention and satisfaction are improved by quicker loading times.

Data Usage and Bandwidth

JavaScript that is not required uses additional bandwidth, which increases data usage for users and website owners.

Users with restricted data plans or those who browse from places with spotty internet connectivity should pay particular attention to this.

Reduced Page Size

Quicker page loading is essential for modern online apps and mobile devices. Smaller page sizes produce this effect. Reducing unneeded JavaScript results in a leaner codebase, which shrinks the size of the entire page.

Better Performance

The browser can interpret and execute JavaScript files more quickly when they are smaller and more focused, which improves the browser’s performance as a whole.

Better Caching

Caching methods may not function properly when JavaScript code changes regularly, resulting in more frequently downloading larger files. JavaScript that isn’t being used can be removed to increase cache effectiveness and decrease pointless server calls.

Improved SEO and page rankings

Search engines rank sites based on a variety of factors, including how quickly a website loads. Websites that load faster are more likely to rank higher in search results, which increases organic traffic.


Reducing unnecessary JavaScript can significantly enhance user experience on mobile devices, where resources and processing power are frequently constrained.

Code Maintainability

Because it adds needless complexity, keeping unneeded JavaScript in the codebase might make it more difficult to maintain and debug the code. Unused code should be removed to make it easier to read and maintain.


Hackers may be able to take advantage of vulnerabilities in unused JavaScript. Unused code should be removed to decrease the attack surface and strengthen website security.

To effectively reduce unused JavaScript, developers can use various techniques like code splitting, tree shaking, and utilizing modern build tools and frameworks that optimize the final output.

By prioritizing website performance, developers can create a better browsing experience for their users, leading to increased engagement and satisfaction.

How do I reduce unused JavaScript on my website?

Reducing unused JavaScript on your website is crucial for improving its performance and user experience.
Here are some steps you can take to achieve this:

  1. Audit Your Code

    Start by carefully examining the JavaScript code on your website. Identify the scripts that are and are not being used. This can be done manually or with the aid of several code analysis tools.

  2. Remove Unused Scripts

    Once you’ve made a list of all the JavaScript files on your website that aren’t being used, delete them. This can be done by eliminating the references to the corresponding scripts from your JavaScript or other files, or by deleting the corresponding script> tags from your HTML files.

  3. Reduce Use of Third-Party Libraries

    Examine the scripts and third-party libraries you are utilizing. If you discover that some are not necessary for the operation of your website, you might want to remove them or exchange them with more compact versions.

  4. Use the tree-shaking

    Make use of the tree-shaking feature if your website employs contemporary JavaScript frameworks or bundlers like Webpack. In order to produce smaller and more optimized bundles, tree shaking is used to remove superfluous code during the construction process.

  5. Lazy loading

    Use lazy loading for JavaScript modules that aren’t required to load when the page first loads. This will shorten the initial load time because they will only be retrieved and executed when necessary.

  6. Async and Defer Attributes

    In your script tags, use the async or defer attributes for scripts that are necessary but not crucial for the first rendering. By doing this, the script doesn’t need to load and run before the browser can continue parsing and producing the page.

  7. Service-Side Rendering

    Instead of depending exclusively on client-side JavaScript for initial content rendering, think about employing server-side rendering (SSR). As a result, less JavaScript may be required to load the initial page.

  8. Use code splitting

    Use code splitting to break up your JavaScript into smaller sections according to functionality. Only the relevant code will be loaded in this manner as users browse your website.

  9. Cache Management

    Implement appropriate caching techniques for your JavaScript scripts. As a result, the server may receive fewer requests overall because returning users can reuse the cached scripts.

  10. Regular Upkeep

    As your website develops, make sure to regularly evaluate and update your JavaScript codebase to eliminate any recently unused scripts and to optimize those that are already there.

By following these steps, you can effectively reduce unused JavaScript on your website, leading to improved performance, faster loading times, and a better user experience.

How to check for unused JavaScript?

Checking for unused JavaScript can be a bit challenging, especially if you have a large codebase. However, there are several methods and tools you can use to help identify and remove unused JavaScript from your website.

Here are some approaches:

  1. Manual Code Review
  2. Code Linters
  3. Browser Developer Tools
  4. Automated Testing
  5. Code Coverage Tools
  6. Webpack Bundle Analyzer
  7. Third-Party Tools

Nevertheless, here are other functions you can learn to enhance your JavaScript skills.


In conclusion, reducing unused JavaScript is a fundamental aspect of web development that brings numerous benefits to both website owners and users. By optimizing code and eliminating unnecessary scripts, developers can achieve faster load times, improved performance, reduced data usage, better caching efficiency, and heightened security.

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