Core Web Vitals

Largest Contentful Paint (LCP) quantifies the duration it takes for the most significant content element on a webpage to load. It signifies the moment when the user can view the main content they came for. As people tend to dislike slowness in life, users also become frustrated with a slow page load. Google has defined specific guidelines for a satisfactory LCP score — optimally, each page on your site should attain an LCP within 2.5 seconds.

What sets LCP apart from other page speed metrics? Consider this analogy: if page speed metrics were likened to a relay race, then LCP would represent the final, most pivotal runner. It’s not just about when the baton is first picked up (First Contentful Paint), but more importantly, when it’s finally passed over the finish line. LCP provides a more accurate representation of when the content the visitor is expecting to see is rendered, making it a more significant measure of user experience.

In the web world, Cumulative Layout Shift (CLS) measures the visual stability of a page, aiming to reduce layout shifts — those annoying, unexpected changes in page layout that often occur when a web page is loading.

A low CLS score guarantees a stable web page that’s user-friendly and free from unpredictable movements and shifts. A website with high CLS can lead to a poor user experience. Typical culprits causing high CLS include images without dimensions, dynamically injected content, and web fonts causing FOIT/FOUT. Identifying and resolving these issues can lead to a significant reduction in CLS, creating a more visually stable and user-friendly website. Web pages with low CLS ensure a smooth, enjoyable user journey.

First Input Delay (FID) gauges the time it takes for a user to interact with a webpage after they’ve signaled their intent to do so, like clicking a button or a link. A low FID means a webpage is quick to respond to user interactions, leading to a more fluid, engaging user experience.

But what happens when there’s a delay? You start feeling impatient, right? When FID is high, users may perceive the page as unresponsive, leading to frustration and potentially causing them to abandon the page. That’s why optimizing FID is crucial for enhancing user experience.

This can be achieved by:

• Reducing JavaScript execution time
• Minimizing third-party scripts
• Using a content delivery network (CDN)
• Optimizing image sizes
• Utilizing browser caching

When it comes to enhancing your LCP, there are various ways to do so, including:

• Image and Video Optimization: Make sure images and videos are in modern formats, compressed, and sized appropriately. Use lazy loading to load them only when needed.
• Server Response Time: Choose a fast web hosting provider, enable server-side caching, and consider using content delivery networks (CDNs) to reduce server response times.
• Efficient CSS and JavaScript: Optimize CSS and JavaScript files by eliminating render-blocking resources, minifying, and compressing them. Use asynchronous loading for non-essential scripts.
• Critical Resource Prioritization: Specify critical resources with the “preload” attribute and load critical CSS early to minimize rendering delays.
• Resource Preloading and Preconnection: Use “preload” and “preconnect” attributes to instruct browsers to load critical resources and establish connections early.
• Content Delivery Network (CDN): Utilize CDNs to distribute content globally and reduce server response times for users in different locations.

To improve the CLS for your website’s Core Web Vitals, focus on addressing the factors that contribute to unexpected layout shifts during page loading, such as:

• Prioritize Image Loading: Ensure that you specify the dimensions of images in your HTML to reserve space for them before they load. Additionally, use the “lazy” loading attribute for images that aren’t immediately visible.
• Minimize Dynamically Injected Content: Avoid adding new content above the existing content, particularly above the fold, once the page has loaded.
• Optimize Font Loading: Use CSS with the “font-display: swap;” property to prevent text from shifting as web fonts load.
• Load Critical CSS Early: Inline critical CSS or load it asynchronously to prevent layout shifts during page rendering.
• Evaluate Third-Party Scripts: Carefully assess and minimize the use of third-party scripts that could trigger layout shifts. Consider using placeholders for third-party iframes.

To optimize FID, focus on improving the interactivity and responsiveness of your web pages, including:

• Efficient JavaScript and CSS: Ensure that your JavaScript and CSS resources are optimized by reducing their file sizes, loading them asynchronously or deferring their loading, and eliminating any unnecessary code.
• Preload Critical Resources: Prioritize the loading of critical resources such as fonts and scripts by using the “preload” and “prefetch” attributes.
• Utilize Browser Caching: Set proper cache headers for your assets to leverage browser caching. Consider using a content delivery network (CDN) to serve static assets from geographically distributed servers for faster loading.
• Efficient DOM Manipulation: Minimize unnecessary DOM manipulation and layout shifts during both page loading and user interactions. Implement smooth animations and transitions using “requestAnimationFrame” to enhance the user experience.
• Progressive Enhancement: Implement progressive enhancement to ensure that the core functionality of your website remains functional even without JavaScript.