Core Web Vitals Checker

Core Web Vitals are Google's three metrics for how a page feels to actually use: how quickly the main content appears, how quickly the page responds when someone interacts with it, and how much it shifts around while loading. They started as a ranking signal and have stayed one, but the more practical reason to care is that slow, jumpy pages lose visitors before they've read a word of your content.

What the checker calculates

This tool measures three things for the URL you give it. Largest Contentful Paint (LCP) is the time it takes for the biggest visible element (usually a hero image or main heading) to render. Interaction to Next Paint (INP) measures how long the page takes to respond after someone clicks, taps or types. Cumulative Layout Shift (CLS) scores how much the page's content moves around unexpectedly as it loads, which is what causes a reader to hit the wrong button because an ad slot loaded late.

How to read the result

Google publishes rough thresholds for each metric, and this is what most tools, including this one, measure against:

A page can pass on two metrics and fail badly on the third, and the third is usually the one worth fixing first. CLS failures are often the cheapest to solve, because they're commonly caused by images or ads without a reserved size.

Lab data versus field data

A checker run on demand, like this one, produces lab data: a single simulated visit under controlled conditions. Google's own ranking signal is based on field data, real measurements gathered from actual visitors over the previous 28 days (the Chrome User Experience Report, or CrUX). The two can disagree, particularly on a page with low traffic or a very mixed audience of desktop and mobile users, because field data reflects real devices and real connection speeds. Treat a lab result as a diagnostic starting point, and check Search Console's own Core Web Vitals report for the field data behind your actual rankings.

When this tool is enough

For a quick check after a template change or before a launch, running a single URL here is the fastest way to catch an obvious regression. For a full audit across hundreds of templates and page types, or to correlate crawl behaviour with performance, a full crawler is the better instrument, and the technical SEO crawlers comparison covers what those tools add. A result from any automated checker, this one included, can be wrong or incomplete for a given page, so treat it as a strong hint rather than a verdict.