The Ultimate Guide to Core Web Vitals

This guide provides an in-depth look at Core Web Vitals, a set of metrics that measure the performance of web pages. It covers the importance of Core Web Vitals, what they measure, and how to improve them.

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Core Web Vitals

As website owners and marketers, it’s important that we prioritize the performance of our websites. After all, a well-performing website means providing visitors with a great user experience and achieving our desired business goals. Core Web Vitals are a set of metrics Google has recently introduced to measure the performance of a website and ensure that it meets the expectations of its visitors. Having a good understanding of these factors and how they affect your website performance is essential to providing a great user experience and improving your website’s performance

In this ultimate guide to Core Web Vitals, we’ll explore the different metrics, explain why they are important, and discuss how you can use them to improve your website performance. From understanding the basics of Core Web Vitals to optimizing your website for the best user experience, this guide will provide the information you need to get the most out of your website.

1. What Are Core Web Vitals?

Core Web Vitals are a set of metrics that measure the user experience on web pages. They are based on real-world usage data and measure key aspects of page loading performance, interactivity, and visual stability. Core Web Vitals measure the loading performance of web pages, how quickly they can respond to user input, and how visually stable they are during and after loading. Additionally, Core Web Vitals is used to help Google explore ways to improve page experiences, making them more enjoyable, efficient, and useful. By understanding how well pages are performing, webmasters can take steps to improve their performance and make the web a better place for everyone.

The three types of Core Web Vitals that are measured are:

LCP measures the loading performance of a page, FID measures the interactivity of a page, and CLS measures the visual stability of a page. By measuring these three Core Web Vitals, allows web developers to get a comprehensive understanding of the performance of their websites. This will, in turn, help them optimize the user experience, as well as increase their website's overall ranking in search engine results.

2. Why Are Core Web Vitals Important?

Core Web Vitals are essential for a successful website since they measure the user experience. These metrics are key indicators of how well a website is performing, providing insights into how content is being delivered to users. It also helps identify areas where a website might be underperforming and guides improvements. It is important for website owners to pay attention to these indicators and take action to improve performance. 

A website can be improved, such as optimizing images, minimizing load times, and minimizing the number of redirects and HTTP requests. All of these elements help to ensure that a website is performing optimally and providing users with the best possible experience. Additionally, Core Web Vitals are being used as part of Google's algorithm to rank websites, making them even more important for website owners.

3. A detailed look at the core web vitals

Largest Contentful Paint (LCP)

Largest Contentful Paint (LCP) is an important web performance metric that measures the time it takes for the largest content element visible within the viewport to load. It is an essential metric for ensuring a good user experience since it measures how quickly the largest element of a page is rendered. As such, it is recommended to measure the LCP of a web page and strive to keep it below 2.5 seconds. Additionally, LCP can be used in combination with other metrics, such as Cumulative Layout Shift (CLS) and Time to First Byte (TTFB), to gain a comprehensive view of the user experience. By understanding LCP and its relationship to other metrics, developers can optimize web performance in order to improve user experience.

First Input Delay (FID)

First Input Delay (FID) is the time elapsed between a user's first interaction with a web page (e.g. clicking a link, entering a text field, etc.) and the time when the browser can respond to that user input. FID is a key metric in determining the performance of a website, as it directly affects the user experience - a slow FID can lead to frustration, loss of engagement, and ultimately, a lower rate of conversion. FID can be improved by limiting the number of scripts and elements that the browser must load when navigating to a page, as well as by leveraging caching and pre-fetching techniques. In short, FID is an important metric to consider when optimizing the performance of a web page and ensuring a positive user experience.

Cumulative Layout Shift (CLS)

Cumulative Layout Shift (CLS) is a metric developed by Google to measure the visual stability of a web page. It is an important metric for website owners to consider when designing and optimizing for user experience. CLS measures how much web page elements shift around on a page as a result of changes in the page layout. It is caused by a variety of factors, including images and ads loading late, dynamic content changing size, and other unexpected layout changes. A high CLS score can be seen as a sign of poor user experience and can result in fewer conversions and higher bounce rates. Optimizing for CLS can help improve user experience, reduce page abandonment, and increase conversions.

4. Comparison 

Field data vs. Lab data

When it comes to measuring page performance, it is important to compare core web vitals field data vs. lab data

  • Field data provides an accurate representation of how users are experiencing the website in the real world, while lab data provides a controlled environment to measure performance metrics. 
  • Field data is collected from real users accessing the website from their device, geographic location, and connection speed. Lab data, on the other hand, can be collected in a controlled environment with a specific device, connection speed, and geographic location. 
  • Field data is a better measure of user experience, while lab data is a better measure of page loading speed. 

It is important to compare both field and lab data when measuring page performance so that you can get a complete picture of the user experience.

Mobile vs. Desktop

  • The Core Web Vitals is a set of metrics that measure the user experience when accessing a website. These metrics can be compared between mobile and desktop devices, allowing for the optimization of user experience for both platforms. 
  • Mobile devices tend to have a lower Largest Contentful Paint (LCP) score than desktop devices since mobile devices have slower download speeds. 
  • However, mobile devices tend to have a higher Cumulative Layout Shift (CLS) score than desktop devices, since mobile devices are more likely to be used on the move, leading to an unexpected shuffling of content. 
  • Mobile devices also tend to have a lower First Input Delay (FID) score than desktop devices. This is due to the reduced size of mobile devices leading to slower input responsiveness. 

Comparing the Core Web Vitals between mobile and desktop devices can help to optimize the user experience for both platforms.

5. How to Monitor Core Web Vitals

Monitoring your website’s Core Web Vitals is essential to ensure that your website is performing at its best. You can use a variety of tools to monitor your website’s performance. Google Search Console provides reports on the performance of your website as well as the Core Web Vitals. You can also use Lighthouse and PageSpeed Insights to audit your website’s performance and Core Web Vitals. Additionally, you can use tools like GTmetrix and WebPageTest to monitor your website’s performance in real-time. By using these tools and staying up to date on the latest changes to Core Web Vitals, you can ensure that your website is optimized for success.

6. Benefits of Improving Core Web Vitals

Improving Core Web Vitals offers a range of benefits to website owners. 

  • It provides a better user experience, which can lead to increased customer retention and higher conversion rates. 
  • It can also improve website speed, which reduces page loading times, allowing users to find the information they need faster. 
  • Additionally, improved Core Web Vitals will give your website a higher ranking on search engine results pages, allowing for higher search engine visibility and more organic traffic. This can help your website stand out from the competition, leading to more website visitors and more conversions. 
  • Finally, improved Core Web Vitals can lead to improved overall website performance, providing a better experience for both users and website owners alike.

7. What Actions to Take to Improve Core Web Vitals 

Once you know what Core Web Vitals you need to improve, the next step is to take action to improve them. This can be challenging, but there are some steps you can take to make the process easier. First, review the page speed report and identify which page elements need to be optimized. Then, work to improve the page speed of those elements as much as possible. Consider using caching, optimizing images, optimizing JavaScript, using browser extensions, and using browser performance testing tools to identify areas where you can improve your Core Web Vitals. Finally, actively track your performance over time and make sure you continue to improve your Core Web Vitals.

8. Best Practices for Core Web Vitals

Best Practices for Core Web Vitals are a set of guidelines to ensure websites are optimized to meet the standards of web performance. It involves optimizing user experience by ensuring page load times are quick, page responsiveness is smooth, and visual stability is maintained. It also involves leveraging caching, leveraging compression, and optimizing images. 

Additionally, optimizing JavaScript and CSS delivery, minifying files, avoiding render-blocking resources, and leveraging browser caching are all important best practices for Core Web Vitals. By following these best practices, websites can ensure they are optimized for optimal performance and that users have a positive experience.


The Ultimate Guide to Core Web Vitals is an invaluable resource for anyone looking to improve their website’s performance. By following the tips and best practices outlined in this guide, you can ensure that your website is optimized to load quickly, provide a smooth user experience, and rank higher in search engine results. With the right optimization strategies, you can be sure that your website is providing the best possible experience for your users, while also increasing your chances of success in the digital space.

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