Core Web Vitals Table
| Vital | Measures | Good | Poor |
|---|---|---|---|
| LCP (Largest Contentful Paint) | Loading speed | ≤ 2.5s | > 4.0s |
| INP (Interaction to Next Paint) | Responsiveness | ≤ 200ms | > 500ms |
| CLS (Cumulative Layout Shift) | Visual stability | ≤ 0.1 | > 0.25 |
| FCP (First Contentful Paint) | First render | ≤ 1.8s | > 3.0s |
| TTFB (Time to First Byte) | Server response | ≤ 800ms | > 1.8s |
Core Web Vitals are the three metrics that Google uses for the Page Experience ranking signal: LCP (loading speed), INP (responsiveness) and CLS (visual stability). All are measured at the 75th percentile of page loads, segmented by mobile and desktop - so your fastest 25% of users don’t mask problems for the slowest 75%.
INP replaced FID (First Input Delay) in March 2024 because FID only measured the first interaction, while INP measures ALL interactions during the page lifetime - a more complete picture of responsiveness.
How to use
- Filter by vital name, metric type, or threshold - loading, interactivity, stability - to find what you need.
- Read the good and poor columns for the exact thresholds that Google uses for ranking.
- LCP and INP affect ranking; FCP and TTFB are diagnostic tools for understanding why LCP is slow.
Frequently asked questions
What replaced FID and why?
INP (Interaction to Next Paint) replaced FID (First Input Delay) in March 2024. FID only measured the delay before the first interaction; INP measures the full latency of every interaction throughout the page lifetime, reporting the worst one at the 75th percentile. This gives a more complete picture of real-user responsiveness.
How can I improve my LCP score?
LCP is usually an image or hero banner. Optimise by: preloading the LCP image (link rel=preload), serving it in modern formats (WebP, AVIF), using a CDN, eliminating render-blocking resources, and ensuring the server responds quickly (TTFB under 800ms). Every 100ms of TTFB improvement shifts LCP by the same amount.
What causes CLS (layout shift)?
CLS happens when content moves after it has been painted: images without width/height attributes, ads injected above content, web fonts causing text to reflow (FOUT), or dynamically inserted content above existing content. Fix by reserving space: set width and height on images, use aspect-ratio CSS, and avoid inserting content above existing content.
Is FCP still important if it is not a Core Web Vital?
FCP (First Contentful Paint) is not a ranking signal, but it is a diagnostic tool: it tells you when the first pixel appears. If FCP is fast but LCP is slow, the problem is the hero image or font loading - not the server response. Use FCP to narrow down where the loading pipeline breaks.