What Are Core Web Vitals?

Core Web Vitals are a set of Google metrics that measure the real-world user experience of a web page, focused on loading speed, interactivity, and visual stability. They are part of Google's broader page experience signals and influence rankings, particularly as a tiebreaker between pages of similar relevance. There are three Core Web Vitals: Largest Contentful Paint, Interaction to Next Paint, and Cumulative Layout Shift.

The Three Core Web Vitals

  • Largest Contentful Paint (LCP): how long the largest visible element takes to load, measuring perceived loading speed. Good is 2.5 seconds or less.
  • Interaction to Next Paint (INP): how quickly the page responds to user interactions, measuring responsiveness. Good is 200 milliseconds or less. INP replaced First Input Delay (FID) as a Core Web Vital in March 2024.
  • Cumulative Layout Shift (CLS): how much the page layout unexpectedly shifts during loading, measuring visual stability. Good is 0.1 or less.

Google measures these from real user data (field data) where available and from lab tools like Lighthouse for diagnostics. Passing the thresholds for all three on most page loads is the target. Because the metrics reflect actual user experience, improving them tends to help both rankings and conversion.

Use Cases

  • Page experience optimization: diagnosing and fixing slow loads, sluggish interactions, and layout jumps to pass the thresholds.
  • Pre-launch QA: testing templates against Core Web Vitals before shipping, so performance regressions are caught early.
  • Competitive benchmarking: comparing your real-world performance scores against competitors for the same query.
  • Rendering-accurate measurement: because the metrics depend on how a page actually loads and renders, measuring them at scale requires executing pages in a real browser environment, the same rendering capability behind tools that load full pages rather than raw HTML.

Frequently Asked Questions

Largest Contentful Paint (good: 2.5s or less) for loading, Interaction to Next Paint (good: 200ms or less) for responsiveness, and Cumulative Layout Shift (good: 0.1 or less) for visual stability. A page should meet all three for most real-world loads.

Yes. Interaction to Next Paint (INP) replaced First Input Delay (FID) as a Core Web Vital in March 2024. INP measures responsiveness across all interactions on a page, not just the first, making it a more complete signal.

They are part of Google's page experience signals and can influence rankings, most often as a tiebreaker between pages of comparable relevance. Strong content still matters most, but poor Core Web Vitals can hold a page back.