What Are Core Web Vitals?
Core Web Vitals are three metrics measuring loading speed, responsiveness, and visual stability. Current thresholds, and a real example.
Core Web Vitals are a set of three specific metrics Google uses to measure real-world user experience on a page: Largest Contentful Paint (loading speed), Interaction to Next Paint (responsiveness), and Cumulative Layout Shift (visual stability). They’re a confirmed ranking factor, though a relatively minor one compared to content relevance and quality.
Why Core Web Vitals matter
Poor Core Web Vitals scores can frustrate visitors into leaving before content even loads, hurting engagement metrics that matter more directly to your business than the ranking signal itself. Google evaluates these at the 75th percentile of real Chrome users over a rolling 28-day window, meaning your Lighthouse score in dev tools can look great while real visitors on slower connections or mid-range phones still fail the threshold. That gap between lab testing and field data is where most sites get caught off guard, a perfect local test result means little if a quarter of actual visitors are experiencing something worse.
The three Core Web Vitals metrics
- LCP (Largest Contentful Paint). Measures loading speed, how long the largest visible element takes to render. Good: under 2.5 seconds.
- INP (Interaction to Next Paint). Measures responsiveness across every interaction on the page. Good: under 200 milliseconds. Replaced First Input Delay (FID) in March 2024.
- CLS (Cumulative Layout Shift). Measures visual stability, how much visible content unexpectedly shifts. Good: under 0.1.
All three must pass at the 75th percentile of real user data for a page to receive an overall “Good” Core Web Vitals assessment. A page failing even one metric drags the overall assessment down.
How to improve Core Web Vitals
- Fix whichever metric is currently “poor” first, then tackle the others, don’t spend time optimizing a metric that’s already passing.
- For LCP: compress and preload hero images, reduce server response time, minimize render-blocking resources.
- For INP: reduce heavy JavaScript execution, break up long tasks, defer non-critical scripts, generally the hardest metric to fix.
- For CLS: reserve explicit space for images, ads, and embeds before they load, avoid inserting content above existing content dynamically.
- Allow several weeks after a fix before judging results, since the CrUX data feeding these scores updates on a rolling 28-day window.
Core Web Vitals thresholds
| Metric | Good | Needs improvement | Poor |
|---|---|---|---|
| LCP | Under 2.5s | 2.5s – 4.0s | Over 4.0s |
| INP | Under 200ms | 200ms – 500ms | Over 500ms |
| CLS | Under 0.1 | 0.1 – 0.25 | Over 0.25 |
Real example
For example, a news site with a slow-loading hero image, a laggy comment box, and ads that shift the layout as they load would likely score poorly on LCP, INP, and CLS respectively, three separate, unrelated technical problems each dragging down the overall Core Web Vitals assessment.
Core Web Vitals and AI search
Core Web Vitals don’t directly influence whether a page gets cited in an AI Overview, that’s driven by content relevance and structure, but page experience still shapes whether a visitor who does click through from an AI-cited link has a good enough experience to stay and engage, an increasingly important consideration as AI-mediated clicks become a larger, more skeptical share of overall traffic.
FAQ
Which Core Web Vital is hardest to fix?
INP, generally. Unlike LCP (usually a resource problem) or CLS (usually a missing-dimensions problem), INP requires deeper JavaScript architecture changes, breaking up long tasks and reducing main-thread blocking.
Where do I check my site’s actual Core Web Vitals scores?
Google Search Console’s Core Web Vitals report shows real user data pulled from the Chrome User Experience Report (CrUX), the authoritative field-data source Google itself uses for ranking evaluation.
Is FID still one of the Core Web Vitals?
No. INP fully replaced First Input Delay as the official responsiveness metric in March 2024. Any current guide still listing FID as a Core Web Vital is outdated.
Can a page rank well with poor Core Web Vitals?
Yes, if content relevance and quality are strong enough. Core Web Vitals function more as a tiebreaker between similarly relevant pages than as a dominant standalone ranking factor.
Related terms
A perfect Lighthouse score means nothing if 25% of your real visitors are still failing the threshold. Check CrUX field data, not your local dev tools, before declaring victory.