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Core Web Vitals: What's the Difference Between Field and Lab Data?

Core Web Vitals measure loading, interactivity, and visual stability. There are two kinds of number: field data (what real visitors actually experienced) and lab data (a single controlled test). They answer different questions and often disagree.

What "Good" Looks Like

Field data is the ground truth of experience but needs enough real traffic to exist — when it doesn't, that's an honest absence, not a zero. Lab data is always available but is one machine, one moment. We show which is which and never present a lab number as lived experience.

We show the meaning and our disclosed bands — never a secret weight or threshold.

Now check your own site

Run the Real Read.

Live check · runs on your site

Check Core Web Vitals — Field vs Lab on a Real Domain

Enter a domain and we'll run the real read — and tell you plainly if the signal isn't there or the page can't be reached.

A real, single-signal read through the same machinery the full scan uses. We report what we can measure and label what we can't.

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