Are users complaining about your slow website? This article shares 7 tricks to take the performance of your website to the moon. Let's get started!

1. Fetch only relevant resources

Did you know you can fetch only the CSS files relevant to the current device?

The link tag has a media attribute that can be used to specify the media query for which the stylesheet is intended.

<link
  rel="stylesheet"
  href="mobile.css"
  media="screen and (max-width: 600px)"
/>

This will fetch the mobile.css file only if the device width is less than 600px.

A live demo of this can be found in w3schools.

2. Minify your code

Minification is the process of removing unnecessary or redundant data without affecting how a resource is processed by the browser. Minification can include the removal of code comments, white space, and unused code, as well as the shortening of variable and function names.

Regardless of the build tool (Webpack, Vite, Snowpack, etc) you use, it would have a minification option. For example, in webpack, you can use the TerserPlugin to minify your code.

3. Pre-fetch resources

You can preload images, CSS, JS, and even entire pages by using the link tag.

<link rel="preload" as="image" href="image.png" />

You can even use quicklink or guess to optimally prefetch resources.

Quicklink is a library that prefetches links in the viewport, using the Intersection Observer API, & makes them load faster, whereas Guess is a library that uses Machine Learning to predict which page the user is most likely to visit next.

4. Use Responsive Images or Art Direction

This is possibly the biggest performance win you can get.

You can use the srcset attribute to specify multiple image sources for different screen sizes. This allows the browser to choose the most appropriate image for the current device.

<img
  srcset="image-480w.jpg 480w, image-800w.jpg 800w"
  sizes="(max-width: 600px) 480px, 800px"
  src="image-800w.jpg"
  alt="some random image"
/>

Art direction is a technique that allows you to serve different images to different devices. This is useful when you want to serve a different image for mobile and desktop devices.

<picture>
  <source
    media="(min-width: 900px)"
    srcset="desktop.jpg"
  />
  <source
    media="(min-width: 480px)"
    srcset="tablet.jpg"
  />
  <img src="mobile.jpg" alt="some random image" />
</picture>

5. Lazy loading of relevant resources

Lazy loading is a technique that allows you to defer the loading of non-critical resources until they are needed.

It just requires you to add the loading="lazy" attribute to the relevant elements and you are good to go.

<img
  src="placeholder.png"
  alt="some random image"
  loading="lazy"
/>

Ideally, you should lazy load images, videos, iframes, and other resources that are not visible on the initial page load.

6. Tree-shake your code

Tree shaking is a term commonly used within a JavaScript context to describe the removal of dead code. It relies on the import and export statements to detect if code modules are exported and imported for use between JavaScript files

Just like minification, tree-shaking & pruning unused code is also a build tool feature.

Here is the webpack documentation on tree-shaking

7. Use Page Speed Insights to detect potential issues

Google's Page Speed Insights is a great tool to detect potential issues with your website.

It not only gives you a score but also provides you with a detailed report of the issues that you need to fix.

That's all folks! 🎉

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Image Credits

1. Web.dev

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FAQ

These are a few commonly asked questions I get. So, I hope this FAQ section solves your issues.

1. I am a beginner, how should I learn Front-End Web Dev?
   Look into the following articles:

   1. Front End Development Roadmap
   2. Front End Project Ideas

2. Would you mentor me?
   
   Sorry, I am already under a lot of workload and would not have the time to mentor anyone.