Core Web Vitals
Core Web Vitals explained
Recommended good values are LCP up to 2.5 seconds, INP up to 200 milliseconds and CLS up to 0.1. Field assessment uses the 75th percentile: three quarters of recorded measurements are at or below that value. Document which page or group, device category and time period are being assessed.
Lab checks help investigate problems under defined conditions. Field data comes from actual use and may show different results. An ordinary Lighthouse page-load report does not measure real user interactions and therefore provides no measured INP for that usage. Good lab results do not replace checks in operation.
PageSpeed Insights uses a trailing 28-day period for its CrUX field data. If a page lacks sufficient data, values for the whole origin may be shown, or field data may be absent. An improvement released today is therefore not fully reflected immediately. Missing data does not automatically mean good or poor performance.
Use the metrics to investigate problems: Does an important image arrive late, does a filter respond slowly, or does a newly loaded element shift the page? Then check the complete journey. Google uses Core Web Vitals in its ranking systems but promises no top position for good values. Nor do they justify fixed revenue gains per millisecond saved.
Examples
Hypothetical application
A product page loads a notice above its after initial display. This shifts the product selection during use. The team reserves appropriate space and retests under the same conditions. It then observes real usage data and checks that the notice remains readable and operable.
Key Points
- Measure loading, input response and visual stability separately.
- Document scope, period and device category.
- Do not equate lab results with field data.
- Assess technical improvement and business impact separately.
Practical application
Check relevant page types and interactions. Identify the source and scope of each measurement, address traceable causes and verify the result in the finished journey.
Useful measures
LCP
Timing of the largest eligible content element appearing in the viewport.
INP
Responsiveness assessed through time from recorded inputs to the next paint.
CLS
Assessment of unexpected layout shifts according to the metric’s rules.
Common mistakes
- Presenting a Lighthouse overall score as a passed field-data assessment.
- Presenting origin-level values as measurements of one URL without identifying the scope.
- Deriving fixed ranking or conversion guarantees from thresholds.
Sources and context
- Google web.dev: Web Vitals
Defines LCP, INP and CLS, recommended thresholds and the distinction between lab and field data.
- Google: About PageSpeed Insights
Describes PageSpeed Insights data scope, lab checks and real-user measurements over a trailing period.
- Google Search Central: Page experience
Places Core Web Vitals in search and explains why good measurements do not guarantee top rankings.
Frequently Asked Questions about Core Web Vitals
No. INP replaced FID as the Core Web Vitals interactivity metric. Interpret older reports accordingly.
No. Unexpected shifts may also happen later during use. Assessment should therefore extend beyond the first page load.
No. They help assess technical obstacles. Sales also depend on the offer, demand, content and other conditions.
Related links
Loading related terms…
All TermsArticles about Core Web Vitals
Predictive Analytics in Marketing: Data-Driven Predictions for Better Decisions
How Machine Learning and Predictive Analytics are revolutionizing marketing decisions, from churn prediction and CLV models to demand forecasting.
Behavioral Data Fusion: How Merging Behavioral Data Is Revolutionizing Marketing
Behavioral Data Fusion connects data streams from web analytics, CRM, social media, and IoT into a holistic customer view. Learn why isolated data silos are marketing's biggest blind spot.
Dark Social: How to Measure and Leverage the Invisible 80% of Your Content Reach
Most of your content is shared through private channels, but invisible to analytics. Here's how to use Dark Social strategically.