Core Web Vitals
Google's essential metrics for measuring user experience on the web.
What are Core Web Vitals?
Core Web Vitals are a set of specific factors that Google considers important in a webpage's overall user experience. They are a subset of Web Vitals and apply to all web pages. Google has stated that Core Web Vitals are part of their ranking algorithm.
As of 2024, the three Core Web Vitals are:
- LCP (Largest Contentful Paint) - Loading performance
- INP (Interaction to Next Paint) - Interactivity (replaced FID in March 2024)
- CLS (Cumulative Layout Shift) - Visual stability
Core Web Vitals Thresholds
| Metric | Good | Needs Improvement | Poor |
|---|---|---|---|
| LCP | ≤ 2.5s | ≤ 4.0s | > 4.0s |
| INP | ≤ 200ms | ≤ 500ms | > 500ms |
| CLS | ≤ 0.1 | ≤ 0.25 | > 0.25 |
The Three Core Web Vitals
Largest Contentful Paint (LCP)
LCP measures the time it takes for the largest content element visible in the viewport to become fully rendered. This is typically a hero image, large text block, or video.
Target: LCP should occur within 2.5 seconds of when the page first starts loading.
Learn how to optimize LCP →Interaction to Next Paint (INP)
INP measures the latency of all user interactions throughout the page lifecycle, reporting the worst interaction (or close to it). A low INP means the page consistently responds quickly to user inputs.
Target: INP should be 200 milliseconds or less.
Learn how to optimize INP →Cumulative Layout Shift (CLS)
CLS measures the total of all individual layout shift scores for every unexpected layout shift that occurs during the entire lifespan of the page. A layout shift occurs when a visible element changes position from one frame to the next.
Target: CLS should be 0.1 or less.
Learn how to optimize CLS →Other Important Metrics
First Contentful Paint (FCP)
Time when the first text or image is painted. Should be under 1.8 seconds.
Time to First Byte (TTFB)
Time for the browser to receive the first byte from the server. Should be under 800ms.
First Input Delay (FID)
Legacy metric (replaced by INP). Measured first interaction delay only.
Speed Index
How quickly content is visually displayed during page load.
How to Measure Core Web Vitals
Field Data (Real Users)
- Chrome User Experience Report (CrUX)
- PageSpeed Insights
- Google Search Console
- web-vitals JavaScript library
Lab Data (Synthetic Testing)
- Lighthouse
- Chrome DevTools
- WebPageTest
- PerfMaster
Why Core Web Vitals Matter for SEO
Since June 2021, Core Web Vitals have been an official Google ranking factor as part of the "page experience" update. Sites that provide a better user experience may see improved search rankings, especially in competitive niches.
Note: Core Web Vitals are one of many ranking factors. Great content remains the most important factor for search rankings.