Core Web Vitals
Google's three user-experience metrics, covering loading, responsiveness and visual stability, that feed into ranking as part of page experience.
In depth
What it really means
Three metrics: Largest Contentful Paint for loading, Interaction to Next Paint for responsiveness, and Cumulative Layout Shift for visual stability. INP replaced First Input Delay in March 2024, which is the change most older articles get wrong.
The ranking effect is real but small, and it acts as a tiebreaker rather than a driver. Nobody outranks better content by being fast. Plenty of people lose conversions by being slow, which is the better reason to care.
How it works
- Real Chrome users send performance data to the Chrome UX Report.
- Metrics are aggregated at the 75th percentile per URL group.
- Pass or fail is assessed against the three thresholds.
- The result contributes a small ranking signal as part of page experience.
Pass thresholds, measured at the 75th percentile of real user visits:
LCP under 2.5 seconds · INP under 200 milliseconds · CLS under 0.1 Field data from real users is what counts for ranking. Lab scores from a testing tool are diagnostic only.
Pros & cons
Pros
- Directly improves conversion rate, which usually beats the ranking benefit.
- Diagnoses real user experience problems rather than proxy metrics.
- Free measurement through Search Console and CrUX.
Cons
- Small ranking effect, frequently oversold.
- Fixes are engineering work, not marketing work.
- Field data lags by 28 days, so improvements take a month to show.
Common mistakes
- Still optimizing for First Input Delay, which was retired in 2024.
- Chasing a perfect Lighthouse score, which is lab data and not what ranking uses.
- Treating it as a major ranking lever when it is a tiebreaker.
- Fixing the homepage only, when templates across the site share the same problems.
Best practices
- Use Search Console field data as the source of truth, not Lighthouse.
- Fix by page template rather than by individual URL.
- Prioritize CLS first. It is usually the cheapest to fix and the most annoying to users.
- Justify the work on conversion rate, not ranking, because that is where the return actually is.
FAQs
What are Core Web Vitals?
Three metrics measuring loading (LCP), responsiveness (INP) and visual stability (CLS), used as part of Google’s page experience ranking signals.
What replaced First Input Delay?
Interaction to Next Paint, in March 2024. INP measures responsiveness across all interactions rather than just the first one, and it is harder to pass.
How much do Core Web Vitals affect rankings?
Modestly. They act as a tiebreaker between pages of similar quality rather than a primary driver. The conversion rate benefit is usually the stronger argument.
Lab data or field data?
Field data, from real Chrome users, is what ranking uses. Lighthouse and PageSpeed Insights lab scores are useful for diagnosis but do not determine your assessment.
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