Core web vitals, also known as website vitals or core website vitals, might be silently killing your website traffic. Despite creating excellent content and building quality backlinks, your site could still be losing visitors because Google prioritizes websites that deliver exceptional user experiences.
Since becoming an official ranking factor in 2021, these core vitals metrics have significantly influenced search visibility. Furthermore, with Google’s 2025 update replacing FID with INP (Interaction to Next Paint), the stakes are even higher. Consequently, understanding and optimizing your web core vitals has never been more crucial for maintaining and growing your website traffic.
This comprehensive guide explains what core web vitals are, how they impact your site’s performance, and importantly, provides actionable solutions to fix common issues. You’ll learn about all three critical metrics, discover the best web analysis tools for monitoring them, and understand exactly how to implement changes that will improve your search rankings and overall web page performance.
What Are Core Web Vitals and Why They Matter
Google’s Core Web Vitals represent a crucial shift in how websites are evaluated in search rankings. These user experience metrics go beyond traditional search engine optimization (SEO) factors to measure what truly matters: the actual experience users have when visiting your site.
Understanding Google’s focus on user experience
In essence, core vitals are standardized metrics that quantify user experience based on factors Google considers necessary for good website interaction. Introduced in 2020, they aim to simplify the landscape and help site owners focus on the metrics that matter most. Unlike traditional SEO factors, these vitals directly measure what users actually experience when interacting with your website. Each metric represents a distinct facet of user experience, is measurable in the field, and reflects real-world experiences of critical user-centric outcomes.
The three key metrics currently making up Core Web Vitals are:
- Largest Contentful Paint (LCP): Measures loading performance. For good user experience, LCP should occur within 2.5 seconds of page load start.
- Interaction to Next Paint (INP): Measures page responsiveness. Good experiences require INP under 200 milliseconds.
- Cumulative Layout Shift (CLS): Measures visual stability. Pages should maintain CLS scores of less than 0.1.
Google believes these core website vitals are critical to all web experiences, which is why they’ve committed to incorporating them across all their popular tools.
How Core Web Vitals became a ranking factor
Initially announced in 2020, core web vitals officially became part of Google’s ranking algorithm in mid-2021 through what’s known as the “Google page experience update.” This update incorporated these metrics into page experience signals that help determine a page’s search ranking. While Google uses hundreds of ranking factors, Core Web Vitals stand out because they’re transparent and measurable. Unlike many black-box ranking factors, you can see exactly how your site performs against these metrics and take concrete steps to improve them. Importantly, Google has confirmed that page experience signals, including Core Web Vitals, do affect rankings in search results. However, relevance remains paramount – if website A is faster than website B, but B is more relevant to the search query, website B would still outrank A. Additionally, the impact follows a sliding scale rather than being binary. Moving from “needs improvement” to “good” may see ranking improvements. Still, websites that are already good and improve speed by just a millisecond or two may not see noticeable changes in SEO performance.
The 2025 update: INP replaces FID
In March 2024, Google made a significant change to core web vitals by replacing First Input Delay (FID) with Interaction to Next Paint (INP). This update addressed known limitations of FID, which only measured the first interaction delay and didn’t reflect the full user experience. The key difference is that while FID only measured the delay of the first interaction, INP captures responsiveness across all interactions throughout a user’s session. This provides a much clearer view of user experience, focusing on how responsive a page is beyond just the first click or tap. For good performance, your INP score should be 200 milliseconds or less. Scores between 200-500 milliseconds need improvement, while anything above 500 milliseconds is considered poor. This metric now plays a critical role in how Google evaluates your site’s overall page responsiveness. To help site owners prepare for this change, Google announced that Search Console would include INP in the Core Web Vitals report, allowing webmasters to monitor and improve this metric before it became an official factor in page experience ranking.
Breaking Down the 3 Core Metrics
Each core vital metric measures a specific aspect of user experience that directly impacts how visitors interact with your website. Understanding these metrics in detail allows you to pinpoint exactly what needs fixing on your site.
Largest Contentful Paint (LCP)
LCP evaluates how quickly the largest content element in the viewport loads and renders. This metric focuses on what users actually see rather than backend loading processes. Essentially, it measures when your page’s main content has likely finished loading. The elements considered for LCP include:
- Images and image elements within SVG
- Video elements (using the poster image or first frame)
- Elements with background images loaded via the url() function
- Block-level text elements containing text nodes
For optimal user experience, your LCP should occur within 2.5 seconds of page load start. Scores between 2.5 and 4 seconds need improvement, while anything above 4 seconds is considered poor. LCP timing can be broken down into four components: Time to First Byte (TTFB), load delay, load time, and render delay. Identifying which component takes longest helps prioritize your optimization efforts to improve loading speed.
Interaction to Next Paint (INP)
INP measures the responsiveness of your website to user interactions throughout the entire page lifecycle. Unlike its predecessor FID, INP evaluates all interactions, not just the first one. The metric captures three key components:
- Input delay: Time waiting for the browser to process the interaction
- Processing time: Running event handlers in JavaScript
- Presentation delay: Time until the browser paints the next frame
Only certain interactions count toward INP: clicks, taps, and keyboard inputs. Scrolling and zooming are excluded. For good user experience, your INP should be under 200 milliseconds. Scores between 200-500ms need improvement, while anything above 500ms is poor. INP was designed to better reflect real user experience since research shows 90% of a user’s time on a page is spent after it loads. Moreover, the final INP value reported is typically the longest interaction observed (with some outliers removed).
Cumulative Layout Shift (CLS)
CLS measures visual stability by quantifying how much page elements unexpectedly move during loading and interaction. A shifting layout frustrates users and can cause accidental clicks. But what is CLS exactly? Cumulative Layout Shift is a core web vital that calculates the sum of all individual layout shift scores for every unexpected layout shift that occurs during the entire lifespan of the page. Common causes of layout shifts include:
- Images without dimensions
- Ads, embeds, or iframes without reserved space
- Dynamically injected content
- Web fonts causing FOIT/FOUT
CLS is calculated by multiplying the impact fraction (how much viewport area is affected) by the distance fraction (how far elements move). For good user experience, maintain a CLS score of 0.1 or less. Scores between 0.1-0.25 need improvement, while anything above 0.25 is poor. Important to note that not all layout shifts count toward CLS. Shifts that occur within 500 milliseconds of user interaction are expected and don’t contribute to the score. Additionally, CLS is measured throughout the entire lifespan of the page, not just during initial load. Understanding these three metrics provides the foundation for diagnosing performance issues on your website.
How Poor Core Web Vitals Hurt Your Website Traffic
Poor performance metrics directly affect your bottom line. Understanding exactly how subpar core web vitals impact your site reveals why optimization isn’t just a technical exercise—it’s a business necessity.
Lower search rankings and visibility
Firstly, Google officially incorporated core web vitals into its ranking algorithm in 2021, making these metrics a direct factor in your search positions. Websites meeting Google’s core web vitals thresholds gain a competitive edge in search results, especially in situations where content relevance is similar between competing sites. Although content relevance and quality remain the primary ranking factors, core web vitals serve as more than just a tie-breaker. They work alongside other signals like mobile-friendliness and HTTPS security to determine your overall page experience score. Notably, for many businesses, this has translated into measurable results—Redbus saw a significant domain ranking uplift across its global market properties after reducing its CLS from 1.65 to 0.
Increased bounce rates and user frustration
Poor core web vitals create frustrating experiences that drive visitors away. According to a 2023 Searchmetrics study, websites meeting Google’s core web vitals thresholds were 24% less likely to experience high bounce rates. This makes perfect sense considering that over 50% of users abandon pages taking more than 3 seconds to load. Real-world examples confirm this relationship:
- NDTV gained a 50% better bounce rate after halving their LCP.
- GEDI saw 77% reduction in CLS and an 8% reduction in bounce rate.
- AliExpress improved CLS by 10 times and doubled their LCP, resulting in 15% lower bounce rates.
The correlation is clear—slow page load speed, unresponsive buttons, and jumping elements frustrate users and prompt them to leave, negatively impacting user engagement.
Reduced conversions and revenue impact
Perhaps most importantly, core web vitals directly affect your revenue. Even minor improvements in website performance can yield substantial financial gains: Just a 0.1-second improvement in site speed has been shown to increase conversion rates by up to 8%. Similarly, eCommerce sites that improve LCP and CLS see up to 15% more conversions based on tests run by major platforms like Etsy and Walmart. The business impact extends across industries:
- Vodafone achieved 11% better cart-to-visit rate and 8% more sales after improving LCP by 31%.
- Cdiscount’s improvements across all three metrics contributed to a 6% revenue uplift during their Black Friday sale.
- Agrofy Market’s 70% better LCP correlated to 76% reduction in load abandonment.
In fact, user experience has become so critical that 83% of customers now consider the experience a company provides as important as its products and services. Accordingly, the data makes a compelling case—core web vitals aren’t just technical metrics but direct drivers of business success or failure.
Tools to Measure and Monitor Your Core Web Vitals
Measuring your core web vitals is the first step toward improving them. Fortunately, Google provides several free web analysis tools that help you identify exactly where your website needs work.
Google PageSpeed Insights
PageSpeed Insights (PSI) combines both lab and field data to give you a comprehensive view of your site’s performance. The field data comes from the Chrome User Experience Report (CrUX), showing how real users experience your site over the previous 28 days. PSI classifies user experiences into three categories: Good, Needs Improvement, or Poor, making it easy to understand your site’s performance at a glance. One major advantage of PSI is that it’s updated daily, whereas other CrUX-based tools are updated monthly. It’s perfect for getting an initial overview of your core web vitals for both a specific page and your entire domain.
Google Search Console
Search Console offers a unique approach by grouping similar pages together in its Core Web Vitals report. This feature helps you identify patterns across your website rather than fixing issues page by page. The report separates mobile and desktop experiences, showing how many URLs are considered “Good,” “Needs Improvement,” or “Poor.” What makes Search Console particularly valuable is that it tells you exactly which core web vital metric (LCP, INP, or CLS) is causing problems on specific groups of pages. This targeted approach helps prioritize your optimization efforts.
Chrome DevTools and Lighthouse
Chrome DevTools provides real-time performance feedback as you make code changes through its Performance panel. This panel offers two valuable views: a live metrics screen showing current core web vitals and a detailed performance profile capturing all page activity. Meanwhile, Lighthouse generates comprehensive reports on LCP, CLS, and Total Blocking Time (a lab proxy for INP). Available directly in Chrome DevTools, as a command-line tool, or through continuous integration workflows, Lighthouse web vitals also highlights potential performance improvements with specific suggestions. These web vitals Chrome tools are essential for conducting a thorough web vitals assessment.
Real User Monitoring (RUM) tools
While synthetic testing is valuable, Real User Monitoring (RUM) captures the actual performance experienced by your site’s visitors. RUM data is what Google uses to determine whether a site meets the recommended core web vitals thresholds. If you don’t already have RUM set up, consider using the web-vitals JavaScript library—a small, modular library (~2KB) that provides a convenient API for collecting Web Vitals measurements. Alternatively, dedicated RUM providers like DebugBear, SpeedCurve, and Datadog offer more comprehensive monitoring solutions to measure web vitals effectively.
CrUX and BigQuery for advanced analysis
For deeper analysis, the Chrome User Experience Report (CrUX) on BigQuery allows you to directly query the full dataset going back to 2017. This enables trend analysis, technology comparisons, and domain benchmarking. The CrUX Dashboard provides visualization without requiring SQL knowledge, offering historical data month over month to track your progress. For teams needing more granular data, BigQuery provides detailed metrics including connection types, device distribution, and even country-level performance. This crux data is invaluable for understanding your website’s performance in real-world conditions.
Actionable Fixes to Improve Your Core Web Vitals
Now that you understand the importance of core web vitals, it’s time to implement practical fixes. Each metric requires specific optimization techniques to achieve meaningful improvements in your web page performance.
Optimizing images and media for LCP
For faster Largest Contentful Paint, always specify width and height attributes on images to help browsers allocate space before loading. Compress images using tools like TinyPNG and convert them to modern formats like WebP for better compression. Most importantly, ensure your LCP image is discoverable in the HTML source—avoid hiding it behind JavaScript or data-src attributes. Proper image optimization can significantly improve your page load speed and overall website performance.
Reducing JavaScript execution for INP
To improve Interaction to Next Paint, break up long JavaScript tasks that exceed 50ms. Implement yielding techniques like scheduler.yield() API to give the browser opportunities to handle critical user interactions. For event handlers, use debouncing and throttling to control execution frequency. Furthermore, minimize unnecessary JavaScript and defer non-critical scripts until after initial page load. These techniques can greatly enhance page responsiveness and user engagement.
Preventing layout shifts for CLS
Maintain visual stability by always including dimensions for images, ads, and embeds. Reserve space for dynamic content using CSS aspect-ratio or min-height properties. For web fonts, consider using font-display: optional to eliminate text layout shifts. Additionally, avoid inserting content above existing elements unless responding to user interaction. By addressing these common causes of layout shift, you can significantly improve your CLS scores and overall web vitals performance.
Using lazy loading and preloading
Strategically implement both techniques—but never lazy-load your LCP image. Instead, add fetchpriority=”high” to prioritize its loading. For non-critical images below the fold, lazy loading reduces initial page weight. Simultaneously, use preload for critical assets like hero images, fonts, and JavaScript needed for important interactions. This balanced approach can greatly improve your overall page load speed.
Implementing a performance budget
Establish clear thresholds for resource usage and load times. Set specific limits like “LCP below 2 seconds” or “image downloads below 1MB.” Performance budgets aren’t roadblocks but guardrails ensuring your team keeps optimization in mind. When facing issues, you can fix them, revert changes, or adjust your budget based on business priorities. This approach helps maintain consistent website performance over time.
Conclusion
Core Web Vitals directly influence your website’s user experience, search rankings, and ultimately your revenue. With the 2025 update replacing FID with INP, maintaining strong responsiveness throughout the user journey has become even more critical, giving well-optimized sites a clear competitive edge. Measuring and improving these metrics is now easier than ever through tools like PageSpeed Insights, Search Console, and WebPageTest.
By optimizing aspects such as image compression, JavaScript execution, and layout stability, businesses can see notable increases in traffic and conversions with relatively small development efforts. Regularly tracking and enhancing your web vitals should be a core part of your SEO strategy to ensure long-term success and deliver a seamless, high-performing experience for your users.