Hey everyone! It’s been a while since I last wrote a blog, and I’ll admit, it makes me a bit sad. The reality is, there’s so much to learn, and sometimes it feels like there’s never enough time to dive into everything. Who am I kidding, though? The truth is, I’ve been procrastinating a lot lately.

But recently, I’ve been exploring web performance—a crucial topic for any frontend developer—and I’m excited to share what I’ve learned. Performance optimization is one of those things that, when done right, can make a world of difference in how users experience your website or web app. Not only does it improve the user experience, but it also boosts SEO and can even impact conversion rates.

So, let’s dive in!

Why Web Performance Matters

In today’s fast-paced world, users expect websites to load quickly and interact smoothly. If your site is slow, users will leave—it's as simple as that. Studies show that a delay of even a few seconds can lead to higher bounce rates and lower engagement. As frontend developers, we’re responsible for ensuring that our applications not only look good but perform well under various conditions.

When it comes to measuring performance, Google is often considered the gold standard. Google provides a set of key metrics, known as Core Web Vitals, that help developers track and improve the performance of their websites. Let’s break them down:

As per the lord Google these things matter in performance

• FCP (First Contentful Paint)
• LCP (Largest Contentful Paint)
• CLS (Cummulative Layout Shift)
• TTI (Time To Interactive)
• INP (Interaction to Next Paint)

Lets Explore them more closely

FCP (First Contentful Paint)

What it Measures: FCP measures the time it takes for the first piece of content (text, images, etc.) to appear on the screen after a user navigates to your page. It’s a critical metric because it gives users feedback that the page is loading. The quicker the FCP, the better the user experience.

How to Improve FCP:

Minimize Render-Blocking Resources: Reduce or eliminate resources that block the rendering of the page, such as synchronous JavaScript or CSS. Use for critical resources.

Defer Non-Critical JavaScript: Use the defer or async attributes for non-essential scripts to ensure they don’t block the initial paint.

*Use Server-Side Rendering (SSR): * SSR helps deliver the initial HTML faster, especially for dynamic content, so that users can see meaningful content sooner.

Optimize CSS Delivery: Minimize the size of your CSS and inline critical CSS, so the browser can render content faster.

Use a Content Delivery Network (CDN): Serve static assets from a CDN to reduce latency and speed up resource delivery.

LCP (Largest Contentful Paint)

What it Measures: LCP focuses on the time it takes for the largest element (typically a hero image, large text block, or video) to fully render within the viewport. It’s a great indicator of perceived load speed, as users consider the page ready once the largest content has loaded. Aim to keep LCP under 2.5 seconds for a fast experience.

How to Improve LCP:

Optimize and Compress Images: Use modern image formats like WebP, compress images, and ensure the right image sizes are served using srcset and sizes attributes.

Lazy Load Below-the-Fold Images: Implement lazy loading for images that aren’t immediately visible to prioritize the loading of above-the-fold content.

Preload Important Resources: Use the tag to load important resources like fonts, hero images, or large media files more quickly.

Minimize Render-Blocking CSS: Just like with FCP, minimize the use of large CSS files that could block rendering.

Reduce Third-Party Scripts: Third-party ads, analytics, or other scripts can slow down LCP. Defer or asynchronously load non-essential scripts.

CLS (Cumulative Layout Shift)

What it Measures: CLS measures the visual stability of your page. Have you ever been reading something, and suddenly the layout shifts, causing you to lose your place or click the wrong button? That’s a bad CLS score. CLS tracks how much elements on the page shift unexpectedly during the load process. A low CLS is essential for smooth user experiences, especially on mobile.

How to Improve CLS:

Set Dimensions for Images and Videos: Always include width and height attributes on images, or use CSS aspect ratio boxes to reserve space for media elements before they load.

Avoid Inserting Content Above Existing Content: Avoid dynamically adding content above existing content unless it’s absolutely necessary (e.g., ads).

Use Font Loading Strategies: When loading custom fonts, use font-display: swap; to avoid layout shifts caused by font loading.

Avoid Injecting New Ads or Popups Without Space: Ensure that dynamically loaded ads, banners, or pop-ups are accounted for in the layout space to avoid unexpected shifts.

Use Image placeholders or loaders with the same space as the image

TTI (Time to Interactive)

What it Measures: TTI measures how long it takes for the page to become fully interactive. This means all buttons, inputs, and links are usable, and the main thread is free to respond to user input. A fast TTI ensures that users can engage with your content quickly without feeling like the site is sluggish or unresponsive.

How to Improve TTI:

Reduce JavaScript Execution Time: Break down large JavaScript bundles and load only essential scripts for the first interaction. Use code splitting in React (with React.lazy()) or dynamic imports in JavaScript.
Use Web Workers: Offload heavy, non-UI blocking tasks to Web Workers to keep the main thread responsive.
Defer Long Tasks: Split long JavaScript tasks into smaller tasks to avoid blocking the main thread for too long.
Preload Critical Resources: Ensure that essential resources needed for interactivity (scripts, styles) are preloaded to avoid delays in TTI.
Optimize CSS and JavaScript: Minify, compress, and prioritize essential code. Use tree-shaking to eliminate dead code and ensure faster script execution. Use GZIP or BROTLI Compression mechanism

INP (Interaction to Next Paint)

What it Measures: A relatively newer metric, INP tracks the time it takes for a page to respond to user interactions (like clicking buttons, scrolling, or typing) and update the UI accordingly. It helps measure overall interactivity beyond just the initial load, ensuring that your app remains snappy throughout the user session.

How to Improve INP:

Reduce Input Latency: Make sure that user inputs (clicks, keypresses) are handled quickly by avoiding long JavaScript tasks that block the main thread.

Prioritize Input Responsiveness: Use requestAnimationFrame or requestIdleCallback to handle non-urgent work during idle time, leaving the main thread open for interaction handling.

Use Debouncing and Throttling: When handling frequent user interactions (like scrolling or typing), debounce or throttle the event handlers to prevent the UI from becoming unresponsive.

Lazy Load Non-Critical Code: Defer loading of non-critical functionality until after the initial interaction.
For instance, you can lazy load components in React using React.lazy() and Suspense.

By following these strategies, you can significantly improve these key metrics and deliver a faster, more responsive user experience. These optimizations, especially when applied together, help ensure your site not only passes Google's Core Web Vitals tests but provides an exceptional experience for your users

I hope you found this blog useful and you were able to get some key insights from it to help in your next performance improvement strategy.

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