Core Web Vitals: How Google Measures Your Site’s User Experience

Google Core Web Vitals are a set of metrics that measure real-world user experience for loading performance, interactivity, and visual stability of a web page. These metrics directly influence Google Search rankings and serve as a benchmark for how visitors perceive your website’s performance.

In this article, we will cover what Core Web Vitals are, how they affect your search rankings, and what you can do to improve them.

What Are Core Web Vitals?

Core Web Vitals are three specific metrics Google uses to analyze a web page’s overall user experience. They function as part of Google’s page experience signals, which also include mobile-friendliness, safe browsing, HTTPS security, and intrusive interstitial guidelines.

Page experience signals measure how users perceive the interaction quality with a web page. Strong Core Web Vitals scores contribute to better visibility in Google Search results, while poor scores can hold your site back from achieving its ranking potential.

The three Core Web Vitals metrics are Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS).

Largest Contentful Paint (LCP)

LCP measures the loading performance of a page. Specifically, it tracks how long after a user requests the URL it takes to render the largest content element visible in the viewport.

The largest element is typically a hero image, video thumbnail, or large block-level text element. This element matters because it signals to visitors that the page is actually loading and delivering content.

Target threshold: LCP should occur within 2.5 seconds of when the page first starts loading.

Interaction to Next Paint (INP)

INP replaced First Input Delay (FID) as the official responsiveness metric in March 2024. While FID only measured the delay before the browser could process the first user interaction, INP provides a more complete picture of responsiveness by measuring all interactions throughout a user’s entire session.

INP tracks three components of every interaction:

• Input delay: The time between when a user interacts and when event handlers begin executing
• Processing time: How long event handler code takes to run
• Presentation delay: The time from when handlers finish until the browser displays the visual update

The final INP score reports the longest interaction observed during a page visit, giving you insight into the worst-case responsiveness your visitors experience.

Target threshold: Pages should have an INP of 200 milliseconds or less. Scores between 200-500ms need improvement, and anything above 500ms is considered poor.

Cumulative Layout Shift (CLS)

CLS measures the visual stability of a page by tracking unexpected layout shifts that occur during the page’s entire lifespan.

A CLS score ranges from zero to any positive number. Zero means no unexpected page shifting occurred, while larger numbers indicate more visual instability. Layout shifts frustrate users when they accidentally click the wrong element because content moved at the last moment.

Target threshold: Pages should maintain a CLS score of 0.1 or less.

Knowing your current scores is the first step toward improvement. Google provides several free tools to measure Core Web Vitals performance.

PageSpeed Insights

PageSpeed Insights analyzes the content of any web page and generates a detailed report with suggestions for improvement. The tool displays both field data from real Chrome users and lab data from simulated page loads.

Enter any URL to see your LCP, INP, and CLS scores alongside actionable recommendations. The main limitation is that each URL must be checked manually.

Google Search Console Core Web Vitals Report

The Core Web Vitals report in Google Search Console shows how your pages perform based on real-world usage data collected from Chrome users.

This report groups URL performance by status (Good, Needs Improvement, Poor), metric type, and URL groups containing similar web pages. Only indexed URLs appear in the report, making it valuable for understanding site-wide performance patterns.

Chrome User Experience Report

The Chrome User Experience Report (CrUX) provides real user experience metrics from Chrome users who have opted in to share anonymized browsing data. This dataset powers the field data shown in PageSpeed Insights and serves as Google’s official data source for Core Web Vitals assessment.

You can access CrUX data through BigQuery for deeper analysis or use it indirectly through PageSpeed Insights and Search Console.

How to Improve Core Web Vitals

If your scores fall below the recommended thresholds, targeted optimizations can bring them into the green zone.

Tips to Improve Loading (LCP)

Common causes of poor LCP scores include slow server response times, render-blocking JavaScript and CSS, slow resource load times, and client-side rendering bottlenecks.

Optimization strategies:

• Remove unnecessary third-party scripts that slow initial page load
• Upgrade to faster web hosting with better server response times
• Implement lazy loading so images only load when users scroll to them
• Use modern image formats like WebP or AVIF with proper compression
• Preload critical resources that appear above the fold
• Use a Content Delivery Network (CDN) to serve assets from locations closer to your visitors

Upgrade to faster web hosting. Server response time directly impacts LCP. If your current host delivers slow Time to First Byte (TTFB), no amount of front-end optimization will compensate. InMotion Hosting’s Performance Servers are built with NVMe SSD storage and server-level caching to help your pages load faster.

Tips to Improve Interactivity (INP)

Heavy JavaScript execution is the primary cause of poor INP scores. When JavaScript occupies the browser’s main thread, it cannot respond to user interactions.

Optimization strategies:

• Break long JavaScript tasks into smaller chunks that yield to the main thread
• Defer non-critical JavaScript until after initial page load
• Remove unused code through tree shaking and code splitting
• Minimize DOM size, as large DOM trees slow down rendering and interaction processing
• Use requestAnimationFrame for animations instead of setInterval
• Consider Web Workers to move heavy processing off the main thread
• Audit third-party scripts and remove any that are not essential
• Implement browser caching to speed up return visits

Tips to Improve Visual Stability (CLS)

Layout shifts typically result from images without specified dimensions, ads and embeds loading without reserved space, dynamically injected content, and web fonts causing invisible text flashes.

Optimization strategies:

• Always include width and height attributes on images and video elements
• Reserve space for ad slots before they load
• Preload fonts and use font-display: optional or font-display: swap to prevent layout shifts during font loading
• Avoid inserting content above existing content after the page has started rendering
• Use CSS transform properties for animations instead of properties that trigger layout recalculations

Why Core Web Vitals Matter for Your Business

Google uses the 75th percentile of real-user data to assess Core Web Vitals. This means at least 75% of your visitors must experience scores within the “good” threshold for your pages to pass.

Sites meeting Core Web Vitals benchmarks tend to rank better in search results, experience lower bounce rates, and see higher engagement metrics. Poor scores create a frustrating user experience that drives visitors to competitor sites with faster, more stable pages.

Improving Core Web Vitals is not a one-time project. Regular monitoring and optimization should become part of your ongoing website maintenance routine. After every significant site update, review your LCP, INP, and CLS metrics and address any regressions before they impact your visitors and search rankings.

For more detailed technical guidance on each metric, visit Google’s official Web Vitals documentation.