What are Core Web Vitals and how do you track them?

Updated July 16, 2026: Core Web Vitals have evolved since this post was first published. Most notably, Interaction to Next Paint (INP) has fully replaced First Input Delay (FID) as the interactivity metric, capturing responsiveness across the entire visit rather than just the first tap. This post has been updated to reflect the current three-metric framework, revised thresholds, and how to track and improve each signal using both Google's free toolset and behavioral analytics platforms like Quantum Metric. An FAQ has also been added to address the most common questions about measurement and optimization.

A shopper taps a product image, waits, and the "Add to cart" button jumps three inches down the page just as their thumb lands. They accidentally hit "Buy now" instead. Frustrated, they close the tab. That tiny moment of visual chaos is exactly what Core Web Vitals were built to measure and prevent.

Back in 2020, Google announced that a new category called "Page Experience" would become an important factor in search engine optimization, or SEO. The measurable heart of that category is a set of metrics Google calls Core Web Vitals.

• Google elevated Page Experience, measured through Core Web Vitals, as an SEO ranking factor alongside structural signals like mobile friendliness, security, and quality content.
• The three current Core Web Vitals are LCP (loading performance), INP (interactivity), and CLS (visual stability), and INP replaced the original First Input Delay (FID) metric.
• Improving Core Web Vitals means optimizing server response times, reducing and deferring JavaScript, sizing images and media well, and managing third-party tools carefully.
• Teams can track Core Web Vitals using tools like the Chrome User Experience Report, PageSpeed Insights, and Google Search Console, often as part of broader SEO audits.
• Quantum Metric measures Core Web Vitals alongside network timings and segments, giving teams deeper insight into the full digital experience.

Core Web Vitals are Google's way of turning something people have always felt — a slow page, a laggy button, a layout that won't sit still — into three metrics you can measure and fix. They sit inside Google's broader page experience signals and shape how your pages rank in Search. Getting them right isn't about chasing a score for its own sake. When a page loads fast, responds instantly, and stays put under a user's thumb, you're rewarding the real person on the other end of the screen and giving Google exactly what its ranking systems reward. This guide breaks down what each metric means, how to track it, and where to focus first.

What are Core Web Vitals? A quick definition.

Core Web Vitals are a set of standardized metrics from Google that measure real-world user experience across three dimensions: loading performance, interactivity, and visual stability. They are a subset of Google's broader page experience ranking signals, and Google recommends good Core Web Vitals for success in both Search and user experience.

For years, Google has placed a premium on websites and web applications that pay close attention to how people actually interact with a page. With so many businesses competing for the first spot on a search results page, sites with standout user experiences now have a better opportunity to pull ahead.

At baseline, your website's UX should be intuitive, easy to use, quick, and leave the user wanting to come back for more. Core Web Vitals put a number on whether you're actually delivering that.

How Core Web Vitals fit alongside existing SEO signals.

Current SEO rankings account for a number of structural factors, such as:

• How mobile-friendly your website is, or how good it looks on a smartphone
• Safe browsing, which means no viruses or phishing attempts
• Up-to-date security certificates
• HTTPS websites over HTTP
• Well-researched or informative content
• Minimal pop-ups and other intrusive interstitial elements, unless a design-savvy tool like Elementor for WordPress creates them

These structural components remain a vital part of your website's success. Previously, SEO focused on an objective analysis of the page, regardless of the value it added for users. Now SEO mixes structure (existing SEO signals) with perceived user benefit (Core Web Vitals).

Factors outside your control can hurt website performance, including device capabilities, poor network conditions, and how a particular user interacts with a page. Focusing on Core Web Vitals, though, reduces the chance that visitors will bounce.

What are the three Core Web Vitals?

The three Core Web Vitals are Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). Each maps to one dimension of experience: LCP measures loading, INP measures interactivity, and CLS measures visual stability.

A quick note on evolution: when this metric set first launched, the interactivity measure was First Input Delay (FID). Google has since replaced FID with INP, which captures interactivity more completely. All three current metrics — LCP, CLS, and INP — are considered stable, meaning Google treats them as essential for great user experiences. Your site should be hitting the 75th percentile in each category across both mobile and desktop devices to stay competitive.

Here are the "good" thresholds Google recommends for each metric:

LCP (Largest Contentful Paint): loading performance.

LCP, or Largest Contentful Paint, is the time it takes for a page's largest batch of content — images and words — to load. In other words, LCP measures how quickly a website loads enough content to look complete. A good LCP is 2.5 seconds or less.

If you want to get more technical, LCP is closely related to First Contentful Paint (FCP) and Time to First Byte (TTFB) measurements.

To boost your LCP score, speed up server response times. You can do this by removing render-blocking JavaScript and CSS, and by ensuring that image files, videos, and other visual elements are high-quality but not oversized.

INP (Interaction to Next Paint): interactivity.

INP, or Interaction to Next Paint, measures interactivity — how responsive your page feels when users click, tap, or type. It quantifies what users feel when they try to interact with the page, and first impressions matter. Websites that load quickly but still exhibit high friction can suffer here. A good INP is 200 milliseconds or less.

INP replaced the earlier First Input Delay (FID) metric, which only measured the delay before the first interaction. INP looks at responsiveness across the whole visit. If you're having issues with your interactivity score, take a look at Total Blocking Time (TBT) and Time to Interactive (TTI) measurements. Reducing JavaScript file sizes helps, since it lowers the time browsers spend processing requests.

CLS (Cumulative Layout Shift): visual stability.

CLS, or Cumulative Layout Shift, measures visual stability — how much visual elements shift while the page is loading. That accidental "Buy now" tap from the intro? Pure CLS. A good CLS is 0.1 or less.

Sudden or unexpected layout shifts lower your CLS score. This can include fonts that render larger or smaller than expected, or third-party ads that continuously resize. CLS often depends on API calls, which in turn depend on third-party tools. Your best bet is to choose your third-party integrations wisely. Under the current SEO scheme, drag-and-drop CMS platforms that take too long to resize images might see their rankings fall significantly.

How do you track Core Web Vitals?

You can track Core Web Vitals with free, field-based tools that measure real-user data without any manual instrumentation. Because SEO is now an integral part of the development process, marketers and developers should work together to monitor and optimize these metrics.

For an easy point-in-time measurement of Core Web Vitals, use tools like the Chrome User Experience Report, PageSpeed Insights, and Google Search Console, which includes a dedicated Core Web Vitals report. All three draw on the Chrome User Experience Report (CrUX), whose data is anonymized and based on real users. Third-party SEO tools like Screaming Frog continue to integrate these measurements as well.

Tips for improving your Core Web Vitals.

Here's a look at some ways to sharpen your Core Web Vitals and strengthen your SEO strategy:

• Gorilla Group, the commerce experience agency, points out that while Core Web Vitals are critically important, other Page Experience factors still matter, including mobile optimization, safe browsing, and more.
• Blast Analytics, a consulting and data science firm, breaks down how organizations should prepare for shifts in the SEO algorithm. Running an SEO audit now keeps your team from getting caught off guard.
• BlueMoon Digital, a Denver-based digital marketing consulting firm, shares tips for boosting your ranking. Because conversion rate optimization (CRO) and UX go hand in hand, a solid user experience directly helps decrease shopping cart abandonment rates.

How Quantum Metric supports Core Web Vitals measurement.

Experience is more than UX. It needs to be measured from an interaction, technical, and behavioral standpoint. Our customers love Quantum Metric because they can understand their customer experience from any level, so adding support for Core Web Vitals measurement just made sense.

You can now measure Core Web Vitals in Page Performance, compare them against network timings, build segments, and more.

How Core Web Vitals become better experiences.

Core Web Vitals turn something users have always felt — a slow page, a laggy button, a layout that won't sit still — into numbers you can act on. LCP watches how fast content loads, INP tracks how responsive the page feels, and CLS keeps your layout from shifting under a user's fingertips. Hit the 75th percentile across all three and you're rewarding real people while giving Google what its ranking systems reward.

Tools like PageSpeed Insights and Search Console show you where you stand today. Pairing those field measurements with behavioral context inside Quantum Metric shows you why a score slips, and exactly where revenue is leaking as a result. That combination is how good scores turn into experiences people actually want to come back to.