Core Web Vitals Monitor
Analyze LCP, INP and CLS for any URL using Google PageSpeed API. Get performance score and improvement recommendations.
What this monitor measures
It queries the PageSpeed Insights API and prefers CrUX field data: LCP, INP and CLS measured in real users' browsers over the last 28 days. Those are what Google ranks with. If the URL lacks the traffic for its own sample it falls back to the origin's, and failing that to lab data, telling you which one you are looking at.
Google uses Core Web Vitals as a tiebreaker signal: if two pages have similar content, the one that delivers a better user experience will tend to rank higher.
How to measure your Core Web Vitals step by step
The monitor needs no access to your site and no script to install: it queries the data Google already holds about your URLs.
- 1
Paste the URLs you want to measure, one per line. Analyse specific pages, not just the homepage: Core Web Vitals are assessed per URL.
- 2
Pick mobile or desktop. Always start with mobile, which is what Google indexes with and where problems show up first.
- 3
Check the source label on each result. If it says lab, that URL lacks enough CrUX traffic and what you are seeing is a simulation — useful for diagnosis, but not your real score.
- 4
Work through the red metrics in order of impact: LCP is usually the most expensive to fix and carries the most weight; CLS is usually the cheapest.
Field data updates on a rolling 28-day window. After a deploy, do not expect the improvement the next day: it takes weeks to show fully.
How to read each metric
LCP measures the time it takes for the largest visual element on the page (usually a hero image or main text block) to render. It is the metric most directly related to the user's perception of speed.
Bueno: ≤ 2.5 seconds — fast experience
Necesita mejora: 2.5s – 4.0s — improvable experience
Malo: > 4.0s — slow experience, negative SEO impact
How to improve:
Optimize and compress images (WebP/AVIF), use lazy loading only for images below the fold, implement a CDN, add preload for the LCP resource, and improve server TTFB.
INP measures the response time from when the user clicks, taps or presses a key to when the browser visually updates the screen. It replaced FID in March 2024. It particularly penalizes pages with heavy JavaScript that blocks the main thread.
Bueno: ≤ 200 ms — immediate response
Necesita mejora: 200ms – 500ms — acceptable but improvable response
Malo: > 500ms — slow response, frustrated users
How to improve:
Split JavaScript into smaller chunks (code splitting), remove unnecessary third-party scripts, use web workers for heavy tasks and prioritize hydration of interactive components.
CLS measures how much visible content shifts unexpectedly during loading. A high CLS causes accidental clicks and a poor user experience. The most common causes are images without defined dimensions, variable-size ads and web fonts that change the layout when they load.
Bueno: ≤ 0.1 — stable page
Necesita mejora: 0.1 – 0.25 — occasional shifts
Malo: > 0.25 — unstable page, very poor experience
How to improve:
Always define width and height attributes on images and videos, reserve space for ads and embeds, use font-display: optional or swap for web fonts, and avoid inserting elements above existing content.
Why field data is sometimes missing
There are two ways to measure Core Web Vitals: lab data (synthetic measurements under controlled conditions) and field data (real measurements from real users collected by Chrome). This tool uses lab data via Lighthouse through the Google PageSpeed Insights API.
Lab data (this tool)
Synthetic measurement run by Lighthouse on Google's servers. Reproducible, immediate and without the need for prior traffic. Ideal for detecting issues and measuring the impact of technical changes before publishing.
Field data (CrUX)
Real data collected from Chrome users over the past 28 days. These are the values Google uses directly as a ranking signal. Available in Google Search Console and PageSpeed Insights when there is enough traffic.
Frequently asked questions about Core Web Vitals
Guides on Core Web Vitals
The validator tells you what is broken. These guides explain why it breaks and how to fix it.
What Are Core Web Vitals: LCP, INP, and CLS Explained
Core Web Vitals are the user experience metrics Google uses as a ranking factor. Learn what each one measures, what thresholds define good performance, and why they affect your rankings.
Read guideHow to Improve LCP: Causes, Diagnosis, and Solutions
Slow LCP is the most common web performance problem. This guide covers the 5 main causes of high LCP, how to diagnose which one is affecting your site, and concrete technical solutions.
Read guideCLS: What Is Cumulative Layout Shift and How to Eliminate It
CLS measures how much the content on your page shifts unexpectedly. High CLS hurts user experience and SEO. Learn how to detect it and eliminate it with concrete technical solutions.
Read guideHow to Improve INP: Causes and Solutions for Interactivity
INP measures the latency of all user interactions on your page. Since March 2024 it replaced FID as the official Core Web Vital. Learn how to diagnose it and reduce it with concrete techniques.
Read guideCore Web Vitals in WordPress: Plugins and Step-by-Step Configuration
Improving Core Web Vitals in WordPress is achievable with the right plugins and correct configuration. A practical guide covering WP Rocket, LiteSpeed Cache, and other tools to pass the "Good" threshold for LCP, INP, and CLS.
Read guidePageSpeed Insights vs Search Console: Why the Data Does Not Match
PageSpeed Insights can show "Good" while Google Search Console marks the same page as "Needs improvement." This is not a bug — they measure two different types of data. Learn how to interpret them correctly.
Read guide