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Free Core Web Vitals Test

Run a Core Web Vitals test on any page and see LCP, layout shift and blocking time graded against Google's own thresholds, with the audits failing behind them. No sign-up required.

How to use the Core Web Vitals checker

1. Paste a page URL

Enter any public page. A bare domain works, the tool adds https for you.

2. Pick mobile or desktop

Mobile is the default because that is what Google grades most sites on.

3. Read the result

You get a performance score, each Core Web Vital graded against Google's thresholds, and the audits failing behind them.

What are Core Web Vitals?

Google Core Web Vitals are three metrics that measure how a page feels to load and use, rather than how fast it is to deliver. They cover loading (Largest Contentful Paint), visual stability (Cumulative Layout Shift) and responsiveness (Interaction to Next Paint).

They exist because traditional speed metrics missed the things that actually annoy people. A page can report a fast load while the text jumps under your thumb as an ad slot fills in, or sit unresponsive for a second after you tap a button. Core Web Vitals were designed to catch exactly that.

Google grades them on field data, collected from real Chrome users over a rolling 28 day window at the 75th percentile. A free Core Web Vitals test like this one runs lab data instead: one simulated load, available instantly, which is what you want while iterating on a fix.

Core Web Vitals thresholds

Google applies these at the 75th percentile of real visits, so three quarters of your visitors need to hit them.

Metric	Good	Poor	What it measures
Largest Contentful Paint (LCP)	2.5s or less	Over 4s	How long the biggest element in view takes to render. Usually a hero image, video or heading.
Cumulative Layout Shift (CLS)	0.1 or less	Over 0.25	How much the page jumps around while loading. Caused by images without dimensions, injected banners and late-loading fonts.
Interaction to Next Paint (INP)	200ms or less	Over 500ms	How quickly the page responds when someone taps or clicks. Replaced First Input Delay in March 2024.
Total Blocking Time (TBT)	200ms or less	Over 600ms	The lab stand-in for INP. Measures how long the main thread was blocked and unable to respond.

Why a passing score can still mean a failed assessment

This is the single most common source of confusion, and it is why core web vitals assessment failed is such a frequently searched phrase. The Lighthouse performance score and the Search Console assessment measure different data.

The score above is lab data: one simulated load, on a throttled connection, from one location. The assessment is field data: real Chrome users, real devices, real networks, aggregated over 28 days. A page can be quick in a clean lab run and still fail for people on three year old phones.

There is a second trap. Search Console groups similar URLs together, so one bad page can mark an entire group as failing. And because the field window is 28 days, a fix you shipped yesterday will not show up for weeks. Use this tool to confirm the fix worked, then wait for the field data to catch up.

How to pass the Core Web Vitals assessment

Most failures come down to four things.

Fix LCP at the source

Preload the hero image, serve it in WebP or AVIF at the size it actually displays, and remove render-blocking CSS above it. Most LCP problems are one oversized image.

Reserve space to kill CLS

Set width and height on every image and embed, reserve space for ad slots and cookie banners, and use font-display: optional or swap with a matched fallback metric.

Cut JavaScript to fix blocking time

Third-party tags are usually the culprit. Audit what each script earns you, defer what is not needed for first render, and drop what nobody reads.

Check the field data, not just this

Google grades you on data from real Chrome users over 28 days, not on a single lab run. Use this test to iterate quickly, then confirm in Search Console.

Frequently asked questions

What are Google's Core Web Vitals?

Core Web Vitals are the three page experience metrics Google uses to measure how a page feels to load and use: Largest Contentful Paint for loading, Cumulative Layout Shift for visual stability, and Interaction to Next Paint for responsiveness. They are part of Google's page experience signals and are reported in Search Console for every site.

What is Core Web Vitals in simple words?

Three questions about your page: did the main content appear quickly, did things stay still instead of jumping around while it loaded, and did it react promptly when someone tapped it. If the answer to all three is yes, you pass. They exist because a page can score well on traditional speed tests and still feel broken to use.

What do Core Web Vitals measure?

LCP measures how long the largest visible element takes to render, so it captures perceived load speed rather than raw server time. CLS measures how much visible content moves unexpectedly during loading. INP measures the delay between a user interaction and the next visual update. Together they describe the experience of using the page rather than the technical speed of delivering it.

How to test Core Web Vitals?

Paste your URL into the tool above for an instant lab test showing LCP, CLS and Total Blocking Time with the failing audits behind them. For the field data Google actually grades you on, open the Core Web Vitals report in Google Search Console, which aggregates real Chrome user data over a rolling 28 day window. Use the lab test to iterate quickly and the field report to confirm.

What is a good Core Web Vitals score?

A page passes when LCP is 2.5 seconds or less, CLS is 0.1 or less, and INP is 200 milliseconds or less. Google applies these at the 75th percentile of real visits, so three quarters of your visitors need to hit those numbers, not just your average visitor. Anything worse than 4 seconds LCP, 0.25 CLS or 500ms INP is graded poor.

What is considered a good Core Web Vitals score?

The same three thresholds apply: LCP at or under 2.5s, CLS at or under 0.1, INP at or under 200ms, each measured at the 75th percentile. The separate Lighthouse performance score out of 100 is a different thing, a weighted blend of several lab metrics. You can score 90 plus in Lighthouse and still fail the assessment on field data, which is why the two should not be confused.

How to pass Core Web Vitals assessment?

All three metrics must hit the good threshold at the 75th percentile of real visits, on both mobile and desktop separately. In practice that means fixing your largest image for LCP, reserving space for anything that loads late for CLS, and cutting third-party JavaScript for INP. Field data updates on a 28 day rolling window, so allow up to a month after a fix before the assessment flips.

Why does my Core Web Vitals assessment say failed even with a high performance score?

Because they measure different things. The performance score is lab data from one simulated load on a throttled connection. The assessment is field data from real Chrome users over 28 days, on real devices and networks. A page can be fast in a clean lab run and still fail for users on older phones or slower connections. A single URL failing can also mark a whole group of similar pages as failing.

Are Core Web Vitals still relevant?

Yes, though their weight is often overstated. They remain part of Google's page experience signals and are still reported in Search Console. Google has been consistent that relevance and content quality outweigh page experience: Core Web Vitals act as a tiebreaker between pages that are otherwise comparable. Fixing them will not lift a page that does not deserve to rank on merit.

What are the limitations of Core Web Vitals?

Lab tools like this one cannot measure INP, because it needs a real person to interact with the page, so Total Blocking Time stands in for it. Lab results also vary between runs on the same URL depending on network conditions. Field data solves both problems but needs enough traffic to report, so low traffic pages may show no data at all. And none of it measures whether the content is any good.

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