- Three metrics: LCP measures the time to display the main content, INP the responsiveness to interactions, CLS the visual stability.
- They rely on real-user data, not a lab test: improving a test score isn't enough.
- Their ranking weight is real but modest: they separate close pages, they don't make up for weak content.
Definition
The Core Web Vitals are three metrics by which Google assesses a page's loading and interaction experience.
Worked example
A site shows an LCP of 3.8 seconds on mobile, above the recommended 2.5-second threshold. The cause is an uncompressed 1.2 MB banner image. After compression and a switch to a modern format, LCP drops to 1.9 seconds, and the gap between ad clicks and landing page views narrows by 12 points.
Orders of magnitude
Google's recommended thresholds are 2.5 seconds for LCP, 200 milliseconds for INP and 0.1 for CLS. They're assessed on the 75th percentile of real visits, not the average.
The most common mistakes
- Optimizing a lab score. Google ranks on field data, which reflects real connections and devices.
- Expecting a spectacular ranking gain. These metrics separate, they don't propel.
- Neglecting CLS. Content that shifts during loading loses conversions well before it costs positions.
Where to find the metric
In Search Console, the Core Web Vitals report, fed by real-user data. PageSpeed Insights gives the detail per URL, with field and lab data side by side.
Frequently asked questions
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