Core Web Vitals Checker
Check the Core Web Vitals performance of any URL using real-world data from the Chrome UX Report (CrUX) and simulated Lighthouse tests. See LCP, INP, CLS, FCP, and TTFB with color-coded pass/fail indicators for both mobile and desktop. All analysis runs through our secure server-side API proxy - no API key required.
Check Core Web Vitals
Enter any URL to analyze its Core Web Vitals using Google PageSpeed Insights (CrUX field data + Lighthouse lab data)
Enter a URL above and click "Check Vitals" to see Core Web Vitals data from Google's Chrome UX Report and Lighthouse.
LCP
Largest
INP
Interaction
CLS
Cumulative
FCP
First
TTFB
Time
Real User Data from CrUX
View actual Core Web Vitals metrics collected from real Chrome users in the field, sourced directly from Google's Chrome UX Report database.
Mobile & Desktop Analysis
Toggle between mobile and desktop views to see how your site performs across different device types, with separate metrics for each.
All Five Core Metrics
See LCP (loading), INP (interactivity), CLS (stability), FCP (first paint), and TTFB (server response) - every Web Vital that Google measures.
Pass / Fail Color Coding
Instantly identify performance issues with green (good), orange (needs improvement), and red (poor) indicators based on Google's official thresholds.
Web Developers
Debug performance bottlenecks in your code. Identify which metrics are failing, then optimize images, scripts, and server config to pass Core Web Vitals.
SEO Specialists
Check if client sites meet Google's page experience ranking signals. Use field data from CrUX to prioritize SEO fixes with the highest ranking impact.
E-commerce Managers
Monitor product page performance. Slow LCP or high CLS directly correlates with lower conversion rates - catch issues before they cost sales.
Agency Owners
Run Core Web Vitals checks across multiple client sites from one interface. Generate performance reports with Google's official data source.
Performance Engineers
Compare lab data (Lighthouse) with field data (CrUX) to identify where synthetic testing diverges from real user experience.
Product Managers
Track Core Web Vitals as part of your product's quality metrics. Make data-driven decisions about performance investments based on real user data.
What Are Core Web Vitals?
Core Web Vitals are a set of real-world, user-centered metrics that quantify key aspects of the browsing experience. Google introduced them as ranking signals in 2021, making them essential for SEO success. They measure loading performance (LCP), interactivity (INP), and visual stability (CLS) - the three pillars of page experience.
How Our Checker Works
Enter any URL and our tool fetches live data from the Google PageSpeed Insights API, which combines field data from the Chrome UX Report (real user measurements) with lab data from Lighthouse (simulated tests). You get both perspectives: how real users experience your site, and how a synthetic test evaluates it under controlled conditions.
Understanding the Metrics
LCP measures loading performance - the time until the largest content element becomes visible. INP measures interactivity - how quickly your page responds to user interactions. CLS measures visual stability - unexpected layout shifts as the page loads. FCP measures when the first content appears, and TTFB measures server responsiveness. Together, they paint a complete picture of user experience.
Google's Thresholds
Each metric has three rating bands: Good (green), Needs Improvement (orange), and Poor (red). These thresholds are defined by Google's Web Vitals program. For example, LCP should occur within 2.5 seconds, INP within 200 milliseconds, and CLS should be less than 0.1. Meeting these targets across all metrics gives you the best chance of passing Google's page experience assessment.
Related Tools
DMARC Record Checker
Check DMARC records for any domain via Cloudflare DNS-over-HTTPS. Validate email authentication policy (none/quarantine/reject), analyse alignment settings (adkim, aspf), and extract reporting addresses (rua, ruf) - free online DMARC record checker.
DNS Leak Test
Check if DNS queries and WebRTC are leaking your real IP outside your VPN tunnel. Detects local IPs via WebRTC STUN requests, checks public IP and geolocation via free APIs, and identifies DNS resolvers - free online DNS leak test.
DNS Record Comparator
Compare DNS records across Cloudflare, Google, and Quad9 nameservers automatically. Detects differences in A, MX, NS, CNAME, TXT, AAAA, and SOA records with severity indicators - free online DNS comparison tool.
Reverse DNS Lookup
Look up PTR records for any IPv4 or IPv6 address via Cloudflare DNS-over-HTTPS. Instantly find the hostname behind any IP address with DNSSEC validation status and query time - free online reverse DNS lookup tool.
Core Web Vitals are a set of metrics introduced by Google that measure real-world user experience on the web. They focus on three key aspects: loading performance (Largest Contentful Paint), interactivity (Interaction to Next Paint), and visual stability (Cumulative Layout Shift). These metrics are used as ranking signals in Google Search.
Our checker uses the Google PageSpeed Insights API to fetch your URL's performance data. This API combines real user field data from the Chrome UX Report (CrUX) - which collects anonymous performance data from millions of Chrome users - with lab data from Lighthouse, a synthetic testing tool that runs a controlled audit of your page.
Field data (CrUX) represents real user experiences collected from actual Chrome browser sessions. It reflects how your site performs under real-world network conditions and device capabilities. Lab data (Lighthouse) is collected in a controlled, simulated environment with consistent network throttling and device settings. Field data is more representative, but lab data helps with debugging.
For LCP (Largest Contentful Paint): Good ≤ 2.5s, Poor > 4.0s. For INP (Interaction to Next Paint): Good ≤ 200ms, Poor > 500ms. For CLS (Cumulative Layout Shift): Good ≤ 0.1, Poor > 0.25. For FCP (First Contentful Paint): Good ≤ 1.8s, Poor > 3.0s. For TTFB (Time to First Byte): Good ≤ 800ms, Poor > 1,800ms.
The Chrome UX Report requires a minimum number of visits to a URL before it includes that URL in its dataset. If your URL has low traffic, is behind a login, or is not publicly accessible, the CrUX database may not have sufficient data. In these cases, our tool will show only Lighthouse lab data, or a message indicating no data is available.
INP (Interaction to Next Paint) measures a page's overall responsiveness to user interactions - clicks, taps, and keyboard presses. It replaced FID (First Input Delay) as a Core Web Vital in March 2024. While FID only measured the delay for the first interaction, INP measures the latency of all interactions throughout the page lifecycle, providing a more complete picture of interactivity.
Mobile results typically show slower performance due to less powerful CPUs, slower network connections, and smaller viewports. Desktop results are usually faster. Google uses mobile-first indexing, so mobile Core Web Vitals are particularly important for SEO rankings. Our tool lets you toggle between both views to compare performance.
You should check Core Web Vitals whenever you make significant changes to your site - especially changes to images, scripts, fonts, or server configuration. For ongoing monitoring, check at least once a month to catch performance regressions early. The Chrome UX Report data is updated daily, but it reflects the previous 28-day rolling average.