Core Web Vitals: Enhance Your Site’s Performance and SEO

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What exactly are Core Web Vitals?

Google is introducing a new “Page Experience Signal” that combines Core Web Vitals with other factors such as mobile-friendliness, safe browsing, and HTTPS to score a user’s experience loading a webpage. Core Web Vitals consist of three metrics: LCP, CLS, and FID. LCP. Core Web Vitals are a set of metrics that measure the performance of a website. They are designed to help webmasters and developers understand how their websites are performing in terms of user experience.

Largest Contentful Paint measures the time it takes for a page’s main content to load, focusing on the render time of the largest visible image or text block. If a site has a large image or video background that takes a long time to load, it may struggle to meet Google’s new guidelines.

CLS, or Cumulative Layout Shift, measures layout instability caused by resources and content being loaded above existing content, such as large images, ads, or sidebar widgets that push down content after it has loaded.

FID, or First Input Delay, measures the delay in processing a user’s input when the browser is busy parsing a large JavaScript file. It quantifies user frustration when the browser cannot respond to a user’s input immediately, even when visual elements have loaded on the screen.

While some studies suggest that improving Core Web Vitals can lead to better rankings, these factors are only considered tiebreakers or small ranking factors. Nonetheless, businesses should focus on improving their Core Web Vitals to provide a better user experience and avoid losing traffic and potential customers due to slow loading or unstable content.

Why Core Web Vitals Are Important

Google emphasized that Core Web Vitals is used as part of its search engine results page (SERP) ranking algorithm. Google uses over 200 ranking factors, but not all of them carry much weight. Core Web Vitals, in particular, are referred to as tiny ranking factors or tiebreakers by Google reps. While improving Core Web Vitals may not result in a significant boost in rankings, they still play a role.

Speed metrics have been a ranking factor for many years, but the impact of the mobile page experience update was uncertain due to a couple of Google core updates during the same period. Some studies suggest a positive correlation between passing Core Web Vitals and better rankings, but these results should be viewed with skepticism. Sites that focus on Core Web Vitals likely also do other things right.

The impact of Core Web Vitals on rankings is difficult to determine due to the many factors involved. While they may not be a significant factor on their own, they are still important to consider in improving user experience and overall website performance.

How To Measure Core Web Vitals

There are several tools available for measuring Core Web Vitals on your website. PageSpeed Insights can diagnose lab and field issues on a page. Lighthouse and Chrome DevTools can help optimize sites locally in the lab by measuring Core Web Vitals and providing actionable guidance on what to fix. The CrUX Dashboard or the Chrome UX Report API can be used for field data or the PageSpeed Insights API for lab data. can offer users guidance on optimization using PageSpeed Insights data.

Lighthouse is an automated website auditing tool that measures several dimensions of user experience quality in a lab environment, including performance and accessibility. The latest version of Lighthouse introduces three new metrics to the report. Two of these new metrics, Largest Contentful Paint and Cumulative Layout Shift, are lab implementations of Core Web Vitals and provide important diagnostic information for optimizing user experience. The third new metric, Total Blocking Time, correlates well with the field metric First Input Delay. All of the products powered by Lighthouse are updated to reflect the latest version.

PageSpeed Insights (PSI) reports on the lab and field performance of a page on mobile and desktop devices, providing an overview of how real-world users experience the page and a set of actionable recommendations on how to improve page experience. PageSpeed Insights and the PageSpeed Insights API have also been upgraded to use Lighthouse 6.0 under the hood and now support measuring Core Web Vitals in both the lab and field sections of the report. The CrUX API is a fast and free way to easily integrate development workflows with the origin and URL-level quality measurement for the field metrics Largest Contentful Paint, Cumulative Layout Shift, First Input Delay, and First Contentful Paint.

So there are several tools available for measuring these metrics including Google PageSpeed Insights (PSI), Lighthouse, and Chrome DevTools Performance Panel which all provide detailed information about each metric as well as suggestions for improving them if necessary. Developers can query for an origin or URL and segment results by different form factors. Even if you don’t have RUM on your site, CrUX can provide a quick and easy way to assess your Core Web Vitals. In summary, Google’s tools are now equipped to measure Core Web Vitals, which is essential for delivering an excellent user experience on the web.

How To Improve Core Web Vitals

To improve Core Web Vitals, website owners can implement five steps to improve their site’s performance.

The first step is to reduce Javascript execution. Poor FID scores indicate that a page interacts with users for over 300 milliseconds, so optimizing and reducing JS execution is crucial to reduce the time between the browser execution of JS code and the page. One way to reduce JS execution is by deferring unused JS and splitting one JavaScript bundle into smaller pieces.

The second step is to implement lazy loading. Lazy loading allows images to load at the precise moment when users scroll down through the page, thereby improving a site’s performance and limiting bandwidth usage, improving SEO, and reducing bounce rates.

The third step is to optimize and compress images. Optimizing images can make a page significantly lighter, thus improving the loading speed, LCP score, UX, and search engine rankings. Compressing images with TinyJPG and using next-generation formats like JPEG 2000, JPEG XR, or WebP can also reduce the page size. In addition, using a Content Delivery Network (CDN) can store content on servers all over the world, allowing images to load faster from the server closest to users.

The fourth step is to provide proper dimensions for images and embeds. CLS scores over 0.1 indicate a website’s pages have unexpected layout shifts. To prevent unexpected layout shifts, website owners can provide proper dimensions for images and embeds.

The final step is to improve server response time. To improve server response time, website owners can reduce the amount of data sent, enable compression, and leverage browser caching.


Core Web Vitals are a set of metrics that measure the performance of web pages. Improving Core Web Vitals is crucial for website owners who want to improve their pages’ user experience and search engine rankings. By following the tips in this article, website owners can ensure their sites are in line with the algorithm update and improve their Core Web Vitals scores from poor to good.

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