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  • Writer's picturePeyman Rajabi

Google Core Web Vitals: Understanding Core Web Vitals and Improving Website Performance

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As we delve deeper into the digital age, website performance and user experience have become paramount. One of the key factors that influence these elements is Core Web Vitals, a set of metrics introduced by Google to measure user experience on the web. Understanding and optimizing for Core Web Vitals is essential for any website looking to improve its performance and search engine rankings. This blog post explores Core Web Vitals, their importance, and actionable strategies to enhance your website’s performance.

What Are Core Web Vitals?

Core Web Vitals are a set of specific factors that Google considers crucial in a webpage’s overall user experience. These metrics focus on three main aspects of user interaction:

  1. Loading Performance (Largest Contentful Paint - LCP)

  2. Interactivity (First Input Delay - FID)

  3. Visual Stability (Cumulative Layout Shift - CLS)

Largest Contentful Paint (LCP)

LCP measures the time it takes for the largest visible content element to load within the viewport. This could be an image, video, or block of text. A good LCP score is considered to be 2.5 seconds or faster. LCP is critical because it reflects how quickly a user can see and interact with the main content of a page.

First Input Delay (FID)

FID quantifies the time it takes for a page to become interactive, measuring the delay between a user’s first interaction (clicking a link, tapping a button) and the browser’s response to that interaction. An optimal FID is less than 100 milliseconds. FID is vital as it gauges the responsiveness of a webpage, ensuring users can engage with it promptly.

Cumulative Layout Shift (CLS)

CLS evaluates the visual stability of a webpage by measuring the unexpected layout shifts that occur during the loading phase. A good CLS score is less than 0.1. Visual stability is important to prevent frustrating user experiences caused by content moving around on the screen.

Importance of Core Web Vitals

Core Web Vitals are integral to the overall user experience and are directly linked to SEO performance. Google has integrated these metrics into its ranking algorithm, emphasizing the importance of a good user experience. Websites that meet the recommended thresholds for Core Web Vitals are likely to rank higher in search results, leading to increased visibility and traffic.

Enhancing User Experience

Core Web Vitals focus on key aspects of user experience, ensuring that webpages load quickly, respond promptly to user interactions, and maintain visual stability. Enhancing these metrics can lead to higher user satisfaction, lower bounce rates, and increased engagement.

Boosting SEO Performance

Google’s emphasis on Core Web Vitals means that optimizing these metrics can significantly impact your SEO performance. Websites that offer a superior user experience are rewarded with higher search rankings, making Core Web Vitals a critical component of any SEO strategy.

How to Improve Core Web Vitals

Improving Core Web Vitals involves a combination of optimizing your website’s performance and enhancing user experience. Here are some actionable strategies for each metric:

Improving Largest Contentful Paint (LCP)

  1. Optimize Images and Videos: Compress and resize images and videos to reduce load times. Use modern formats like WebP for images and MP4 for videos.

  2. Enable Lazy Loading: Implement lazy loading for images and videos to ensure they load only when they enter the viewport.

  3. Reduce Server Response Times: Use a reliable hosting provider, enable caching, and optimize server configurations to reduce response times.

  4. Minimize CSS and JavaScript Blocking: Remove unused CSS and JavaScript, and defer non-critical CSS and JavaScript to improve load times.

Enhancing First Input Delay (FID)

  1. Optimize JavaScript Execution: Minimize JavaScript execution time by splitting long tasks and reducing the number of third-party scripts.

  2. Use a Content Delivery Network (CDN): Distribute content through a CDN to reduce latency and improve response times.

  3. Implement Web Workers: Use web workers to run scripts in the background without affecting the main thread, improving interactivity.

Reducing Cumulative Layout Shift (CLS)

  1. Specify Size Attributes: Define size attributes for images and videos to prevent layout shifts as the page loads.

  2. Use Transform Animations: Prefer transform animations over layout-changing animations to ensure stability.

  3. Preload Key Resources: Preload fonts and other critical resources to prevent shifts caused by late-loading assets.

Tools for Measuring Core Web Vitals

Several tools can help you measure and monitor Core Web Vitals, providing insights and recommendations for improvement:

  1. Google PageSpeed Insights: Offers a detailed analysis of your website’s performance, including Core Web Vitals scores.

  2. Lighthouse: A Chrome DevTools tool that audits web pages and provides performance insights, including Core Web Vitals.

  3. Google Search Console: Provides reports on Core Web Vitals for your site, helping you identify and fix issues.

  4. Web Vitals Chrome Extension: Allows you to measure Core Web Vitals in real-time as you browse your website.

Common Mistakes to Avoid

Ignoring Mobile Performance

Many users access websites via mobile devices, making mobile performance crucial. Ensure that your site is optimized for mobile by using responsive design, optimizing images for mobile, and testing mobile performance regularly.

Overlooking Third-Party Scripts

Third-party scripts can significantly impact performance. Regularly audit and remove unnecessary third-party scripts, and load critical scripts asynchronously to minimize their impact.

Not Prioritizing Above-the-Fold Content

Ensure that above-the-fold content loads quickly by prioritizing it in your HTML structure and deferring non-critical resources. This can improve LCP and overall user experience.


Core Web Vitals are essential metrics for assessing and improving website performance. By understanding and optimizing for LCP, FID, and CLS, you can enhance user experience, boost SEO performance, and stay ahead in search rankings. Regularly measure your Core Web Vitals using the recommended tools and implement the strategies outlined in this guide to ensure your website meets Google’s standards.


What are Core Web Vitals? Core Web Vitals are a set of metrics introduced by Google to measure user experience on a webpage, focusing on loading performance (LCP), interactivity (FID), and visual stability (CLS).

Why are Core Web Vitals important for SEO? Core Web Vitals are important for SEO because Google uses them as a ranking factor. Websites that provide a better user experience by meeting these metrics are likely to rank higher in search results.

How can I improve my LCP score? You can improve your LCP score by optimizing images and videos, enabling lazy loading, reducing server response times, and minimizing CSS and JavaScript blocking.

What tools can I use to measure Core Web Vitals? Tools like Google PageSpeed Insights, Lighthouse, Google Search Console, and the Web Vitals Chrome Extension can help you measure and monitor Core Web Vitals.

What is the ideal FID score? An ideal FID score is less than 100 milliseconds. This ensures that your webpage is responsive and users can interact with it promptly.

How do I reduce CLS on my website? Reduce CLS by specifying size attributes for images and videos, using transform animations, and preloading key resources to prevent layout shifts.

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