What Are Core Web Vitals? Key Metrics That Influence SEO Rankings

Core Web Vitals (CWV) are a set of essential performance metrics used by Google to evaluate a webpage’s user experience. These metrics influence both SEO rankings and visitor engagement, making them crucial for any website aiming for top search visibility.

Google introduced Core Web Vitals as part of its Page Experience update to ensure users have fast, stable, and responsive interactions with web pages. The three key CWV metrics are:

Largest Contentful Paint (LCP): Measures how quickly the main content of a page loads, with an ideal target of 2.5 seconds or less.
Interaction to Next Paint (INP): Assesses the responsiveness of a website by tracking user interactions, which should occur in 200 milliseconds or less.
Cumulative Layout Shift (CLS): Evaluates visual stability by detecting unexpected content shifts; a good score is 0.1 or lower.

With Google prioritising user experience in search rankings, optimising these metrics is essential for maintaining high visibility and conversion rates.

Why Core Web Vitals Matter

Impact on Search Rankings and Page Experience Signals

Google uses Core Web Vitals as a direct ranking factor to assess the overall user experience of a website. While high-quality content and backlinks remain essential, page speed, responsiveness, and visual stability can tip the scales in competitive search results.

The Page Experience algorithm evaluates how well a site performs in real-world conditions, considering mobile-friendliness, HTTPS security, and intrusive interstitials alongside CWV. Pages that meet the recommended thresholds for LCP, INP, and CLS are more likely to rank higher, especially when competing against websites with similar content quality.

Google prioritises user satisfaction, meaning a site that loads quickly, responds instantly, and remains visually stable offers a better experience, leading to improved search visibility.

Influence on User Engagement and Conversions

A slow, unresponsive, or unstable website frustrates visitors, increasing bounce rates and reducing conversions.

Studies show that 53% of users abandon a site if it takes longer than three seconds to load. Likewise, an INP delay can make users feel the site is unresponsive, leading to fewer interactions with forms, buttons, and checkout pages.

A stable layout is equally important—unexpected shifts in content can result in accidental clicks, creating frustration and mistrust. By improving Core Web Vitals, businesses can see higher engagement, longer session durations, and increased revenue from better-performing pages.

Breakdown of Core Web Vitals Metrics

Largest Contentful Paint (LCP)

LCP measures how long it takes for the largest visible content on a webpage to fully load. This could be an image, video, or text block that dominates the user’s screen. A fast LCP ensures that visitors can engage with the content almost immediately, improving their experience.

The ideal benchmark for LCP is 2.5 seconds or less. Pages that take longer may struggle to retain visitors, leading to increased bounce rates.

Several factors contribute to slow LCP, including large, uncompressed images, slow server response times, and render-blocking JavaScript or CSS. Poor hosting and excessive third-party scripts can also delay loading times.

Interaction to Next Paint (INP)

INP evaluates how quickly a website responds to user interactions, such as clicking a button or typing in a form field. Unlike its predecessor, First Input Delay (FID), INP considers all interactions throughout a session, not just the first one.

A good INP score is 200 milliseconds or less. Delays beyond this make the site feel sluggish and unresponsive, frustrating users and reducing engagement.

Common causes of poor INP include heavy JavaScript execution, inefficient event handling, and an overloaded main thread. Excessive third-party scripts can also slow down response times.

Cumulative Layout Shift (CLS)

CLS measures how much a webpage’s content moves unexpectedly while loading. This ensures a stable, predictable experience for users, preventing accidental clicks and disruptions.

A CLS score should be 0.1 or lower to be considered good. Anything higher indicates significant visual instability, which can frustrate users and affect usability.

Layout shifts often occur due to missing width and height attributes on images, dynamically injected content, and ads or pop-ups that appear late. Poor font loading practices can also cause shifts, making the page content jump unexpectedly.

Measuring Core Web Vitals

Understanding how well your website performs requires accurate data. Core Web Vitals can be measured using several tools that provide insights into real-world user experience and technical performance.

Google PageSpeed Insights

PageSpeed Insights analyses individual pages, offering both lab and field data. It assigns a performance score and highlights areas that need improvement. This tool breaks down metrics like Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift, helping webmasters prioritise optimisations for faster load times and better responsiveness.

Google Search Console CWV Report

For a broader view, the Core Web Vitals report in Google Search Console tracks CWV performance across an entire website. It categorises URLs into “Good,” “Needs Improvement,” or “Poor,” based on real-user data collected over 28 days, helping site owners identify widespread issues.

Lighthouse and Chrome DevTools

Lighthouse is an open-source tool integrated into Chrome DevTools, allowing developers to run in-depth audits on performance, accessibility, and SEO. It simulates user interactions, identifying delays in page responsiveness and visual stability.

CrUX (Chrome User Experience Report)

CrUX provides real-world performance data collected from users browsing with Chrome. Unlike lab tools, it reflects actual browsing conditions, including device types and network speeds, making it invaluable for diagnosing performance bottlenecks.

How to Improve Core Web Vitals

Enhancing Core Web Vitals requires strategic optimisation to improve page load speed, responsiveness, and stability. By focusing on specific areas, websites can deliver a smoother experience and perform better in search rankings.

Optimising LCP

A slow Largest Contentful Paint (LCP) often results from delayed server responses, unoptimised images, and render-blocking resources. To improve LCP, reduce server response times by using fast hosting and a Content Delivery Network (CDN).

Caching frequently accessed content minimises load delays, while minifying and deferring CSS and JavaScript prevents unnecessary rendering blocks. Additionally, using modern image formats like WebP and AVIF significantly reduces file sizes without compromising quality.

Enhancing INP

Interaction to Next Paint (INP) depends on how efficiently a site processes user interactions. Reducing JavaScript execution time and deferring non-critical scripts prevents excessive main-thread blocking.

Breaking up long tasks ensures the browser remains responsive, improving the user experience across interactive elements like forms and buttons.

Fixing CLS

A poor Cumulative Layout Shift (CLS) score is caused by unexpected content movement. To prevent this, always define size attributes for images, videos, and iframes to ensure space is reserved before they load.

Preloading fonts eliminates sudden reflows, while reserving space for dynamically loaded ads and elements prevents disruptive page shifts.

Common Mistakes to Avoid

Optimising Core Web Vitals is essential, but many website owners make common mistakes that limit their improvements. Avoiding these pitfalls ensures long-term success in both rankings and user experience.

Ignoring Mobile Performance in Favour of Desktop

With over 60% of global web traffic coming from mobile devices, prioritising mobile performance is crucial. Many websites focus on desktop optimisation, overlooking mobile-specific issues like slow load times, heavy scripts, and unresponsive design.

Since Google uses mobile-first indexing, poor mobile performance can negatively impact search rankings, even if the desktop version performs well.

Over-Reliance on Lab Data Instead of Real-User Field Data

Lab tools simulate performance under controlled conditions, but they do not reflect actual user experiences. Core Web Vitals rely on field data, which accounts for real browsing conditions, such as device type, network speed, and user interactions.

Relying solely on lab data can lead to misleading optimisations that fail to address real-world performance issues.

Focusing on Only One CWV Metric While Neglecting Others

Improving LCP, INP, or CLS in isolation does not guarantee a better user experience. For example, optimising page load speed while ignoring interaction delays can still result in poor usability.

A balanced approach ensures all three Core Web Vitals contribute to a seamless browsing experience.

Not Monitoring Performance Consistently

Web performance is not static—changes in content, scripts, and third-party integrations can gradually degrade Core Web Vitals. Without regular monitoring, issues can go unnoticed until rankings and engagement drop.

Using automated tools to track CWV scores ensures early detection and continuous optimisation, preventing long-term setbacks.

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Conclusion

Core Web Vitals are a crucial part of modern SEO, directly influencing search rankings and user experience. A well-optimised website not only ranks higher but also keeps visitors engaged, leading to better conversion rates and lower bounce rates.

Focusing on LCP, INP, and CLS ensures your site loads quickly, responds instantly, and remains visually stable. Ignoring these factors can result in frustrated users and lower search visibility. Regular monitoring and continuous optimisation are essential, as new content, design changes, and third-party scripts can gradually impact performance.

SEO is no longer just about keywords and backlinks—user experience is now a defining factor. Search engines reward websites that prioritise speed, responsiveness, and stability.

By consistently improving Core Web Vitals, you future-proof your website, enhance engagement, and maintain a competitive edge. The key to success lies in testing, refining, and staying ahead of Google’s evolving ranking signals.

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Frequently Asked Questions (FAQs)

Q:What are Core Web Vitals and why are they important for SEO?

A. Core Web Vitals are a set of three performance metrics Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS) used by Google to assess real-world user experience on web pages. These vitals help determine how fast, responsive, and visually stable a site is. Optimising them is important because they influence Google’s search rankings and directly affect how users interact with your site.

Q: How can I check my website’s Core Web Vitals scores?

A. You can check your site’s Core Web Vitals using tools like Google PageSpeed Insights, Search Console, Lighthouse, and Chrome DevTools. These tools provide detailed insights and suggestions for improving each metric using real-user or simulated performance data.

Q: What is a good Core Web Vitals score?

A. For optimal performance:

LCP should be 2.5 seconds or less
INP should be 200 milliseconds or less

CLS should be 0.1 or lower
Meeting or exceeding these benchmarks means your site offers a strong user experience.

Q: Can improving Core Web Vitals boost my website traffic?

A. Yes, indirectly. While Core Web Vitals are not the most powerful ranking signals, they can improve rankings when content quality is equal between competitors. Additionally, faster and more stable sites lead to better user retention, lower bounce rates, and higher conversion rates all of which contribute to increased traffic over time.

Q: Do Core Web Vitals affect mobile and desktop rankings equally?

A. Yes, but separately. Google evaluates Core Web Vitals independently for mobile and desktop devices. Since mobile-first indexing is standard, mobile performance often has a greater impact on rankings. It’s important to optimise your site for both to ensure a consistent experience across all devices.

Veronica Lim

Veronica is the co-founder of digital marketing agency CEO Solutions and has over 20 years of experience launching successful products for leading Fortune 100 MNCs such as Intel, Motorola Solutions, Honeywell and Philips Lighting. She believes SEO is the most sustainable and cost-effective strategy for many Singapore businesses to attract qualified and ready-to-buy customers, bringing them the revenue they need to make their businesses even more successful.

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