What Are Core Web Vitals (CWV)?

Kristian Ole Rørbye

By: Kristian Ole Rørbye

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Core Web Vitals (CWV) are specific factors that Google considers important in a webpage’s overall user experience. These metrics are part of Google’s broader initiative to ensure that the web remains user-friendly, focusing on real-world user experience rather than just the content relevance of a page. Introduced as part of Google’s “Page Experience Update” in 2020, Core Web Vitals have since become crucial in determining a webpage’s search engine ranking. Understanding and optimizing for these metrics is essential for anyone involved in digital marketing, web development, or SEO.

The Three Core Web Vitals Metrics

Core Web Vitals are composed of three primary metrics: Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). Each of these metrics targets a specific aspect of the user experience, aiming to provide a more comprehensive view of a website’s performance.

  1. Largest Contentful Paint (LCP)LCP measures loading performance and refers to the time it takes for the largest visible element in the viewport to load. Unlike older metrics that only measured the time it takes for a page to begin loading, LCP focuses on the point at which the main content has likely loaded. This metric is important because it directly correlates to how fast users feel a page is useful.
    • Good LCP: An LCP of 2.5 seconds or less is considered good.
    • Needs Improvement: An LCP between 2.5 seconds and 4 seconds indicates that the website could perform better.
    • Poor LCP: An LCP of more than 4 seconds is considered poor, suggesting that the page takes too long to load its main content.
  2. First Input Delay (FID)FID measures interactivity, specifically the time from when a user first interacts with a page (like clicking a link or button) to the time when the browser is actually able to respond to that interaction. This metric is crucial for websites where user engagement is a key factor, such as in e-commerce sites or interactive web applications.
    • Good FID: An FID of less than 100 milliseconds is considered good.
    • Needs Improvement: An FID between 100 milliseconds and 300 milliseconds means that the website could improve.
    • Poor FID: An FID over 300 milliseconds is considered poor, indicating noticeable lag that could frustrate users.
  3. Cumulative Layout Shift (CLS)CLS measures visual stability and is used to quantify how much the layout of the page shifts during its lifecycle. Layout shifts occur when visible elements move around unexpectedly, which can lead to poor user experiences and accidental clicks. CLS is especially important for users on mobile devices, where such shifts can be more pronounced due to smaller screens.
    • Good CLS: A CLS score of less than 0.1 is considered good.
    • Needs Improvement: A CLS score between 0.1 and 0.25 indicates that there is room for improvement.
    • Poor CLS: A CLS score greater than 0.25 is considered poor, suggesting that layout shifts are likely affecting user experience negatively.

Why Core Web Vitals Matter

Core Web Vitals are crucial for several reasons. First, they directly impact user experience. Pages that load quickly, are responsive to user input, and remain visually stable tend to provide better experiences, which can lead to increased user satisfaction, higher engagement, and better conversion rates. Secondly, Core Web Vitals are now a significant factor in Google’s search ranking algorithm, meaning that optimizing for these metrics can directly affect a website’s visibility and traffic.

1. User Experience

A webpage that scores well on Core Web Vitals provides a smoother, more enjoyable experience for users. This is particularly important for retaining visitors and reducing bounce rates. For example, a slow-loading page (poor LCP) or one that is unresponsive (high FID) can frustrate users and cause them to leave the site prematurely.

2. SEO and Search Rankings

Since Google’s algorithm update, Core Web Vitals have become a part of the ranking signals used by Google Search. Websites that perform well on these metrics are more likely to rank higher in search results. While content quality and relevance remain the most critical factors, having a website that provides a good user experience can give businesses a competitive edge.

3. Mobile Optimization

With the increasing use of mobile devices, Core Web Vitals also emphasize the importance of optimizing websites for mobile users. Factors like LCP, FID, and CLS are especially relevant for mobile browsing, where slower connections and smaller screens can exacerbate poor performance.

How to Improve Core Web Vitals

Improving Core Web Vitals involves a combination of optimizing website performance and enhancing the overall user experience. Here are some strategies to consider for each metric:

Improving LCP

To improve Largest Contentful Paint, focus on optimizing server response times, utilizing a Content Delivery Network (CDN), compressing images, and deferring non-critical JavaScript and CSS.

Improving FID

To reduce First Input Delay, minimize the amount of JavaScript and defer or delay unnecessary scripts. This can help ensure that the main thread is free to respond quickly to user interactions.

Improving CLS

To reduce Cumulative Layout Shift, use size attributes on images and videos to ensure that the browser allocates the correct amount of space while they load. Avoid inserting content above existing content, except in response to user interactions.

Tools for Measuring Core Web Vitals

Several tools can help measure and analyze Core Web Vitals to understand how a website performs in these areas:

  • Google PageSpeed Insights: This tool provides a Core Web Vitals report, offering suggestions for improving page performance.
  • Lighthouse: An open-source, automated tool for improving the quality of web pages, which includes insights into performance and best practices.
  • Google Search Console: Offers a Core Web Vitals report that helps site owners identify areas of improvement based on real-world data.

Understanding Core Web Vitals and their impact on both user experience and SEO is essential for anyone involved in website development and digital marketing. By focusing on these metrics, businesses can create websites that are not only more user-friendly but also better optimized for search engines.

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