Core Web Vitals Checker
Free Core Web Vitals check for LCP, CLS, and INP on mobile and desktop via PageSpeed Insights. See Good thresholds and fix CWV issues fast — no login.
- Enter page URL
- Pick mobile or desktop
- Apply PSI recommendations
- Browser-based — no install
- Instant results
Submit a URL and choose mobile or desktop. The tool calls Google PageSpeed Insights and returns Lighthouse performance scores plus LCP, INP, CLS, and related lab metrics, with CrUX field data when Google has enough real-user history. This Core Web Vitals checker shows whether your page passes Google's Good thresholds on mobile and desktop.
By Faisal YUpdated
What are Core Web Vitals?
The Core Web Vitals Checker pulls LCP, CLS, and INP for any URL from the Google PageSpeed Insights API. It shows field data from the Chrome User Experience Report (CrUX) when available, plus lab data from a controlled simulation. Google's Good thresholds are LCP under 2.5s, CLS under 0.1, and INP under 200ms. Needs Improvement and Poor bands sit above those marks. Mobile and desktop are shown separately because a page can pass one and fail the other.
When should you use this checker?
Use it when Search Console flags failing Page Experience, before a redesign launch, and after shipping image or JavaScript changes. Unlike a generic speed score, this view isolates the three metrics Google uses for ranking decisions so you know which bottleneck to fix first.
How we check this (worked example)
A product page returns mobile field LCP 3.8s (Needs Improvement), CLS 0.02 (Good), INP 140ms (Good). Lab data points at a 1.2MB hero JPEG as the LCP element. Fix path we use: compress/convert the hero to AVIF/WebP with explicit width/height, defer non-critical JS, re-test until mobile LCP is under 2.5s in lab, then wait for CrUX to refresh. If CLS fails instead, we look for ads and late-injected banners without reserved space before touching LCP images.
How to read field vs lab data
Field data is what Google uses for ranking — real devices and networks. Lab data is for debugging when field data is missing or slow to update. A page passes only when all three metrics are Good in field data for the form factor you care about. Always fix the worst field metric first; pairing this tool with the PageSpeed Checker and Image Size Checker speeds up the diagnosis.
Frequently Asked Questions
What are Core Web Vitals?
Core Web Vitals are three Google metrics that measure real-world page experience: Largest Contentful Paint (LCP) measures loading speed, Cumulative Layout Shift (CLS) measures visual stability, and Interaction to Next Paint (INP) measures responsiveness. Google uses these as ranking factors in its Page Experience system.
What are the Core Web Vitals thresholds for Good?
Google's Good thresholds are: LCP under 2.5 seconds, CLS under 0.1, and INP under 200 milliseconds. Needs Improvement ranges are LCP 2.5–4s, CLS 0.1–0.25, and INP 200–500ms. A page must meet all three Good thresholds in field data to pass the Core Web Vitals assessment in Google Search Console.
What causes a high LCP score?
LCP above 2.5 seconds is most commonly caused by unoptimised hero images (large file size or wrong format), render-blocking CSS and JavaScript that delays the page from painting, slow server response times (TTFB above 600ms), and resources loaded from slow third-party origins. Optimising the LCP image and eliminating render-blocking resources typically yields the largest gains.
What causes Cumulative Layout Shift?
CLS above 0.1 is typically caused by images and video elements without explicit width and height attributes, web fonts causing a flash of unstyled text that shifts content on load, dynamically injected ads or banners that push down existing content, and late-loading widgets that displace page elements after initial paint.
What is INP and how is it different from FID?
Interaction to Next Paint (INP) measures the time from any user interaction (click, tap, keyboard input) to when the browser next paints a response. It replaced First Input Delay (FID) as a Core Web Vital in March 2024 because INP measures all interactions throughout a page session, not just the first one, giving a more complete picture of responsiveness.
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