Core Web Vitals: A Beginner’s Guide

11 Jun 2024 | 9 min read
Core Web Vitals: A Beginner’s Guide

What are Core Web Vitals?

Core Web Vitals are three key metrics that assess a webpage’s speed, interactivity, and visual stability. They play a crucial role in search engine optimization (SEO), and enhancing these metrics can improve your website’s search ranking and user experience.

These metrics are essential ranking factors for search engine optimization (SEO). Improving Core Web Vitals can help your website rank higher in search results and provide a better user experience. Focusing on these areas makes your website faster, more responsive, and easier to use, making it more attractive to users and search engines.

Core Web Vitals are specific factors that Google considers essential for a web page’s overall user experience. They are part of Google’s larger initiative to ensure that web pages provide a great user experience. Core Web Vitals are a subset of Web Vitals, metrics related to speed, responsiveness, and visual stability.

In the digital world, things change quickly. Keeping up with the latest trends helps you know what new tools and techniques are available to improve your website’s performance. It also enables you to understand what users expect from websites in your industry. Staying updated with industry trends is essential because it helps keep your website relevant and effective. As Google updates its algorithms and user expectations evolve, knowing the latest trends ensures you can adapt quickly. This enables you to maintain a solid online presence, attract more visitors, and keep your audience engaged.

The Three Core Web Vitals

Core Web Vitals comprise three primary metrics that help measure a website’s performance. The first is the Largest Contentful Paint (LCP), which measures how quickly the main content of a page loads. The second is the First Input Delay (FID), which looks at how quickly the page responds to the first user interaction. The third is Cumulative Layout Shift (CLS), which checks the visual stability of the page, ensuring elements don’t move around unexpectedly as the page loads.

Largest Contentful Paint (LCP)

LCP measures how long a page’s primary content takes to load. This is important because users want to see something functional quickly. If a page takes too long to load, users might leave. A good LCP score is under 2.5 seconds.

First Input Delay (FID)

FID measures the time it takes for a page to respond to a user’s first interaction, like clicking a link or tapping a button. Quick response times make the website feel more interactive and smooth. A good FID score is less than 100 milliseconds.

Cumulative Layout Shift (CLS)

CLS measures how much the page layout shifts as it loads. Unexpected movements can be annoying and lead to a poor user experience. For example, it can be frustrating if you are about to click a button and it moves. A good CLS score is less than 0.1.

These three metrics are essential for providing a good user experience. By focusing on LCP, FID, and CLS, you can ensure your website is fast, responsive, and stable.

Why Google Included Core Web Vitals

Enhancing User Experience

Google aims to promote websites that provide an excellent user experience. Core Web Vitals focus on critical aspects like loading speed, interactivity, and visual stability, directly impacting how users perceive and interact with a site.

Performance Metrics

Core Web Vitals provide quantifiable metrics (LCP, FID, CLS) that help web admins measure and improve their site’s performance in a standardized way.

Mobile Web Performance

With the increasing use of mobile devices, ensuring good performance and user experience has become crucial. Core Web Vitals address critical aspects of mobile 


Data-Driven Improvements

By integrating these metrics into its ranking algorithm, Google encourages webmasters to prioritize data-based improvements, which leads to a better overall web ecosystem.

Alignment with SEO Goals

Core Web Vitals align with broader SEO goals by ensuring that websites are content-rich and technically optimized for performance, leading to better search rankings and user satisfaction.

History & Journey of Core Web Vitals

Developing and implementing Core Web Vitals are part of Google’s ongoing efforts to improve web performance and user experience. Here’s a detailed timeline tracing the evolution of these metrics:

Early Efforts in Web Performance

  • Page Speed Insights (2010): Google launched Page Speed Insights to help web admins understand and improve page loading times. This tool provided insights into various aspects of web performance and suggested improvements.
  • Mobile-Friendly Update (2015): Known as “Mobilegeddon,” this update prioritized mobile-friendly websites in search results, reflecting the growing importance of mobile web performance and user experience.
  • Introduction of Lighthouse (2016): Google introduced Lighthouse, an open-source automated tool for improving the quality of web pages. Lighthouse audits web performance, accessibility, SEO, and adherence to best practices, providing a comprehensive overview of a website’s quality.

Growing Emphasis on Speed and User Experience

  • Speed Update (2018): Google’s Speed Update made page speed a ranking factor for mobile searches. This update highlighted the critical role of fast-loading pages in delivering a good user experience.

Introduction and Evolution of Core Web Vitals

  • Core Web Vitals Announcement (May 2020): Google introduced Core Web Vitals as a set of specific metrics designed to measure critical aspects of user experience on the web. These metrics included: Largest Contentful Paint (LCP)First Input Delay (FID)Cumulative Layout Shift (CLS).
  • Page Experience Update Announcement (May 2020): Alongside the introduction of Core Web Vitals, Google announced the Page Experience Update, which would incorporate Core Web Vitals into its ranking signals. This update aimed to highlight pages that offer a great user experience in search results.
  • Page Experience Update Rollout (June 2021): Google began rolling out the Page Experience Update, officially integrating Core Web Vitals into its ranking algorithm. This update reinforced the importance of user experience in SEO and encouraged web admins to prioritize these metrics.

Continuous Improvement and Tools

  • Web Vitals Extension and Tools (Ongoing): Google released various tools and extensions, such as the Web Vitals Chrome extension, to help developers and web admins measure and improve their Core Web Vitals scores.
  • Ongoing Adjustments and Updates: Google continues to refine and adjust Core Web Vitals metrics and thresholds based on evolving web standards and user expectations. Regular updates to tools like Lighthouse and PageSpeed Insights provide the latest recommendations and best practices.

Why is Core Web Vital Needed? 

Improved Search Rankings

Google uses Core Web Vitals as a ranking factor. Websites with good scores are more likely to appear higher in search results, which means more visibility and traffic from search engines.

Better User Experience

Core Web Vitals measure critical aspects of user experience. By optimizing these metrics, your website will load faster, respond quicker, and be more stable, keeping users happy and engaged.

Reduced Bounce Rates

Users leave quickly when a website loads slowly or is hard to interact with. Good Core Web Vitals scores can reduce bounce rates by providing a smoother and more enjoyable experience.

Higher Conversion Rates

A better user experience leads to higher conversion rates. If your website loads quickly and is easy to use, visitors are likelier to take desired actions, like purchasing or signing up.

Competitive Advantage

Websites with excellent Core Web Vitals stand out from the competition. If your site performs better than others in your industry, you can attract and retain more visitors.

Increased Mobile Usability

Core Web Vitals are especially important for mobile users. Mobile devices often have slower connections and less processing power. Optimizing for Core Web Vitals ensures your site works well on all devices.

Enhanced Brand Perception

A fast and reliable website enhances your brand’s reputation. Users associate positive experiences with professional and trustworthy brands, which can lead to greater loyalty and word-of-mouth referrals.

Better Engagement Metrics

Suitable Core Web Vitals lead to better engagement metrics, such as longer session durations and more pages viewed per visit. This indicates that users find your site valuable and enjoyable to use.

Compliance with Google’s Best Practices

Following Core Web Vitals guidelines ensure compliance with Google’s best practices for web performance. This helps with SEO and aligns your site with industry standards.

Long-Term Benefits

Investing in Core Web Vitals provides long-term benefits. As user expectations and search algorithms evolve, having a well-optimized site ensures you stay ahead of changes and maintain strong performance.

How to Improve Core Web Vitals

Improving Core Web Vitals is critical to making your website faster and more user-friendly. Here’s how to enhance each of the three primary metrics: LCP, FID, and CLS.

Improve Largest Contentful Paint (LCP)

To make your website load faster, focus on these areas:

  • Optimize Images: Compress images and use the correct size. This helps them load quickly.
  • Upgrade Hosting: To speed up your site, choose a faster server or use a Content Delivery Network (CDN).
  • Remove Render-Blocking Resources: Minimize or defer JavaScript and CSS files that slow down your page loading.
  • Optimize Fonts: Use modern font formats and load them efficiently.

Enhance First Input Delay (FID)

For better interactivity, consider these tips:

  • Minimize JavaScript: Reduce the amount of JavaScript on your site to make it respond faster to user actions.
  • Optimize Third-Party Scripts: Limit and optimize third-party scripts to prevent delays.
  • Use Browser Caching: Store frequently accessed data in the browser to speed up load times.
  • Break Up Long Tasks: Split long tasks into smaller chunks to keep the page responsive.

Improve Cumulative Layout Shift (CLS)

To ensure visual stability, follow these steps:

  • Set Size Attributes: Specify size attributes for images, videos, and other elements to prevent unexpected shifts.
  • Reserve Space for Ads: Allocate space for ads and embeds to avoid layout changes when they load.
  • Avoid Adding Content Above Existing Content: Ensure new content is added below the fold to maintain layout stability.
  • Use Transform Animations: I prefer using transform animations over layout changes to keep elements stable.

Implementing these strategies can significantly improve your Core Web Vitals, leading to a better user experience and higher search rankings. Regularly monitor your site’s performance using tools like Google PageSpeed Insights and Lighthouse to keep your site optimized.

Tools to Measure and Optimize Core Web Vitals

You must measure and optimize Core Web Vitals regularly to keep your website 

performing well. Here are some tools that can help:

Google PageSpeed Insights 

Google PageSpeed Insights is a free tool that analyzes your website’s performance. It provides a detailed report on LCP, FID, and CLS, along with suggestions for improvement. Enter your website URL, and the tool will show you how well your site performs and how you can improve it.


Lighthouse is an open-source tool from Google that helps you improve the quality of your web pages. It runs a series of tests on your site and provides a report on various performance metrics, including Core Web Vitals. You can access Lighthouse through Chrome DevTools or as a standalone tool.

Web Vitals Extension 

The Web Vitals Chrome Extension is a handy tool for real-time monitoring of Core Web Vitals. Once installed, it provides instant feedback on LCP, FID, and CLS as you browse your website, allowing you to spot and fix issues quickly.

Google Search Console 

Google Search Console includes a Core Web Vitals report that shows how your site performs over time. It highlights pages that need improvement and provides insights into specific issues affecting LCP, FID, and CLS. This tool is essential for ongoing website optimization.


GTmetrix analyzes your website’s speed and performance. It offers insights into various metrics, including Core Web Vitals, and provides actionable recommendations to enhance your site. GTmetrix also allows you to test your site from different regions and devices.


WebPageTest is another powerful tool for measuring website performance. It provides in-depth analysis and visualizes Core Web Vitals metrics. You can test your site from multiple locations and browsers, helping you understand how different users experience your website.

Using these tools, you can monitor your Core Web Vitals and make necessary improvements. Regular monitoring and optimization ensure your website remains fast, interactive, and stable, leading to a better user experience and higher search rankings.

Improving your website’s Core Web Vitals is essential for providing a fast, responsive, and stable user experience. Monitor your site’s performance regularly and make necessary adjustments to stay ahead.

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