Performance / Field Data
Core Web Vitals & INP Checker
Real users, not a lab. This reads the Chrome UX Report — the same 28-day field data Google ranks on — so it can measure INP, which no single server-side test ever can.
Field data covers the last 28 days. Pages with little traffic have no URL-level data — the tool falls back to your whole origin and says so.
Lab tests cannot measure INP
INP measures how long the page takes to respond after a real person taps or clicks. Nobody clicks during a synthetic test, so a lab tool can only guess at it — and INP is the Core Web Vital most sites fail. This tool reads Google's field data instead: real Chrome users, real interactions, the 75th percentile, which is the number the ranking signal uses.
What each metric means
LCP — Largest Contentful Paint
How long until the main content is visible. Good is 2.5 seconds or less. Usually a server, image or render-blocking problem.
INP — Interaction to Next Paint
How long the page takes to respond after a tap or click. Good is 200 ms or less. Usually long JavaScript tasks blocking the main thread.
CLS — Cumulative Layout Shift
How much the layout jumps while loading. Good is 0.1 or less. Usually images or ads without reserved space.
TTFB and FCP
Supporting diagnostics, not Core Web Vitals themselves. A slow TTFB pushes every other metric out, and it also makes AI crawlers give up on a page.
Frequently asked questions
Why does this differ from a speed test?
A speed test loads the page once from one machine on one connection — that is lab data. This is field data: what actually happened to real Chrome users over 28 days, aggregated at the 75th percentile. Google ranks on the field data, so when the two disagree, this one is the one that counts.
Why is there no data for my URL?
CrUX only reports a URL once it has enough traffic to be statistically sound and anonymous. Most individual pages never reach that bar, so the tool falls back to origin-level data — your whole site averaged — and labels it clearly.
What is the 75th percentile?
It is the experience of the slowest quarter of your visitors. If your p75 INP is 300 ms, then 75% of interactions were faster than that and 25% were slower. Google uses p75 so that a fast median cannot hide a badly broken minority.
Why do I fail on one metric but pass overall in another tool?
Google requires all three Core Web Vitals to be good at once. One poor metric fails the assessment. This tool refuses to give a verdict at all when any of the three is missing, rather than implying a pass from partial data.
How is this different from your Page Speed Snapshot?
Page Speed Snapshot fetches the page from our server and measures what that one fetch saw — real TTFB, transfer size, compression, render-blocking. It is instant and works for any URL, but it cannot see real users and structurally cannot measure INP. Use that for diagnosis and this for the verdict.