Core Web Vitals checker

Real Lighthouse and field data from Google PageSpeed Insights for your live URL: performance score, LCP, INP and CLS, with your server response time measured separately.

Measuring rankings in

Runs the full audit on your live site. Your report opens in your dashboard.

What this checks

This calls Google PageSpeed Insights for your URL on the mobile strategy and reports the Lighthouse performance score along with LCP, CLS and total blocking time. Where Chrome has enough real traffic on your site it also returns field data, the 75th percentile of what actual visitors experienced, which is the version that counts. Separately we measure your server response time ourselves, because that number is yours alone and is not diluted by anything the browser does afterwards.

Why it matters

Core Web Vitals is a live ranking input, and more practically it is a measure of whether people stay. It is also the audit area where invented numbers are most common, so this check either returns real data or returns nothing: when PageSpeed Insights is unavailable the result is marked as not measured rather than being filled with an estimate that would quietly change your score.

How to read a bad result

A Lighthouse score under 50 is a failure and between 50 and 89 is a warning, with one large caveat attached to both: read the field data first wherever it exists, because the lab half is a simulation of a throttled phone on a shared machine and it disagrees with itself between runs. If there is no field row, you are looking at a model of your page rather than a measurement of your visitors, and the honest thing to take from it is whether the page is structurally heavy rather than what its LCP is.

Speed is a tiebreaker, and the audit is what tells you whether you are in a position to be tied. A page a crawler cannot reach does not benefit from a fast LCP, and in our own measurements of professional sites the access and attribution checks failed far more often than this one did.

All 36 checks, free Plans

A failing result, and what it costs

The same URL, unchanged, tested twice within a few minutes. This is our own page, and the spread is not unusual.

One page, one afternoon, no change between the runs, and a lab LCP spanning the entire scale from comfortably passing to clearly failing. The simulation runs on a shared machine and the throttling model amplifies whatever contention it finds; Lighthouse documents this variability itself. With no field data there is nothing to correct it against, so the honest reading is that this page is not structurally slow and the number is a simulation. The failure this causes is not technical, it is a week spent optimising the tool.

run 1   performance 78    LCP 1.2 s (lab)   CLS 0.00
run 2   performance 41    LCP 4.6 s (lab)   CLS 0.00
field   — not enough real traffic to report

How to fix it

Read the field data first, if there is any.It is the 75th percentile of real Chrome visits over 28 days. If it exists, it is the answer and the lab number is a diagnostic.
Never compare two single lab runs.Not before and after, not against a competitor. Run several on each side and compare medians, or do not use lab data for the comparison at all.
Use lab data for what it is reliably good for.A structurally slow page is slow in every run. It will not tell you your LCP is 2.9 seconds; it will reliably tell you a two-megabyte hero image is why it is not fast.
Fix the causes in order.LCP is nearly always an image too large, lazily loaded, or discovered late. CLS is reserving space. INP is long JavaScript tasks, usually third-party.

Questions people ask

What are good Core Web Vitals scores?

Largest Contentful Paint under 2.5 seconds, Interaction to Next Paint under 200 milliseconds, and Cumulative Layout Shift under 0.1, all measured at the 75th percentile of real visits rather than on your own machine.

Why is there no field data for my site?

Chrome only reports field data once a URL has enough real traffic to be reported without identifying anyone. New and low traffic pages fall back to lab scores, which is normal and not a fault.

Do Core Web Vitals really affect rankings?

Yes, as a tiebreaker rather than a lever. They rarely move a page past better content, and they decide close calls, and they have a direct effect on conversion that has nothing to do with Google at all.