Core Web Vitals
Core Web Vitals are Google's three core metrics (LCP, INP, and CLS) for measuring the quality of a page's user experience. They quantify loading speed, interaction responsiveness, and visual stability, and are used in Google Search's page experience assessment.
- Core Web Vitals measure page user experience through three metrics: LCP (loading), INP (responsiveness), and CLS (visual stability).
- The "good" threshold for each is LCP within 2.5 seconds, INP within 200 milliseconds, and CLS at or below 0.1, evaluated at the 75th percentile of real-user data on mobile and desktop.
- On March 12, 2024, INP officially replaced the former FID (First Input Delay) as the responsiveness metric.
- Because Google factors Core Web Vitals into search rankings as part of its page experience signals, they warrant ongoing attention from an SEO standpoint.
Overview
Core Web Vitals are Google's three core metrics for measuring how smoothly a page actually performs for real users. Going beyond raw page speed, they separately quantify how quickly content paints to the screen, how fast the page responds to user input, and how much screen elements shift unexpectedly. Evaluation is based on field data and is judged separately for mobile and desktop using the 75th-percentile value across page loads.
Metric Thresholds
| Metric | What It Measures | Good Threshold |
|---|---|---|
| LCP (Largest Contentful Paint) | Loading performance — when the largest content element is painted | Within 2.5 seconds |
| INP (Interaction to Next Paint) | Interaction responsiveness — the delay from input to the next screen render | Within 200 milliseconds |
| CLS (Cumulative Layout Shift) | Visual stability — the cumulative amount of unexpected layout movement | 0.1 or below |
For all three metrics, the rating of "good / needs improvement / poor" is determined not by a single measurement of one page but by the 75th-percentile value across real-user loads.
INP's Replacement of FID and Its Role as a Ranking Signal
The responsiveness metric was originally FID (First Input Delay), but FID measured only the delay of the first input and therefore did not fully capture a page's overall interaction experience. To address this limitation, INP — which considers every interaction on a page — was introduced, and as of March 12, 2024, INP replaced FID and was officially adopted as a Core Web Vital. On the same day, FID was removed from Google Search Console, while other tools such as PageSpeed Insights and CrUX applied a six-month phased deprecation period (sources: web.dev, Google Search Central).
Google uses Core Web Vitals in search rankings as part of its page experience signals and states that they align with what its core ranking systems aim to reward. That said, they are not a standalone, absolute factor that determines rank on their own; they work alongside other signals such as content relevance. Google actively recommends achieving good Core Web Vitals for better search performance (sources: Google Search Central, Core Web Vitals documentation).
Implementation Checklist
- Improving LCP — preload critical images and fonts, reduce server response time, eliminate render-blocking resources, and optimize image formats.
- Improving INP — split up long JavaScript tasks, reduce main-thread occupancy, and trim unnecessary third-party scripts to cut input response delay.
- Improving CLS — set explicit width/height or aspect-ratio on images, videos, and ad slots, prevent layout shifts during font loading, and reserve space for dynamically inserted content.
- Monitoring field data — regularly review real-user 75th-percentile values via PageSpeed Insights, the Core Web Vitals report in Search Console, and CrUX.
- Checking mobile and desktop separately — since the two environments are rated independently, confirm that each meets the thresholds.