Core Web Vitals are three metrics Google uses to measure real-world page experience, based on actual visitor data rather than lab simulations.
Largest Contentful Paint (LCP) measures loading speed — specifically, how long it takes for the largest visible element (usually a hero image or heading) to render. The passing threshold is under 2.5 seconds.
Interaction to Next Paint (INP) measures responsiveness — the time between a user’s interaction (click, tap, keypress) and the browser visually responding. It replaced the older First Input Delay (FID) metric in March 2024 because it captures every interaction on the page, not just the first. The passing threshold is under 200 milliseconds.
Cumulative Layout Shift (CLS) measures visual stability — how much content unexpectedly jumps around as a page loads (think: a button shifting right as you’re about to tap it). The passing threshold is under 0.1.
These aren’t scored from a single visit — Google evaluates them using the Chrome User Experience Report (CrUX), a rolling 28-day dataset of real Chrome users, at the 75th percentile. That means at least 75% of your visits need a “good” score for a page to pass.
INP is currently the hardest of the three metrics for most sites to pass, since fixing it usually requires reducing heavy JavaScript execution rather than a quick settings change.
How to check your Core Web Vitals
- Search Console → Core Web Vitals report: groups similar URLs and shows which groups are Good, Need improvement or Poor, separately for mobile and desktop.
- PageSpeed Insights: shows field data for a single URL (if it has enough traffic) plus a Lighthouse lab test with specific suggestions.
- Chrome DevTools → Performance panel: shows live LCP, INP and CLS values as you interact with the page, which is the fastest way to debug INP.
New or low-traffic pages may not have enough CrUX data. In that case Google falls back to data for the whole origin, so site-wide problems still matter.
How to improve LCP
- Find the LCP element (PageSpeed Insights names it). It's usually the hero image or main heading.
- Compress the image, serve it in WebP or AVIF, and add
fetchpriority="high". - Don't lazy-load the LCP image, and don't inject it with JavaScript.
- Reduce server response time with caching and a CDN.
- Remove render-blocking CSS and JavaScript from the
<head>.
How to improve INP
- Break up long JavaScript tasks (anything over 50 ms) so the browser can respond to taps between them.
- Delay or remove heavy third-party scripts such as chat widgets, heatmaps and tag-manager bloat.
- Give instant visual feedback (a pressed state or spinner) before running expensive work after a click.
- Avoid very large DOMs. Pages with thousands of elements are slow to update.
How to improve CLS
- Set
widthandheight(oraspect-ratio) on every image, video and iframe. - Reserve fixed space for ads, cookie banners and embeds.
- Don't insert content above existing content after the page loads, unless the user triggered it.
- Use
font-display: swapwith a fallback font of similar size to limit text jumps.
How much do Core Web Vitals affect rankings?
Core Web Vitals are part of Google's page experience signals. They are confirmed ranking factors, but relevance and content quality matter far more. A fast page with weak content will not outrank a slower page that answers the query better. Treat good vitals as a tie-breaker and, more importantly, as a conversion lever: faster, stable pages keep more visitors and sell more.
After you fix something
Lab scores update immediately, but field data uses a rolling 28-day window. Use "Validate fix" in the Search Console report, then expect about four weeks before the status changes. Keep a simple log of what you changed and when, so you can link improvements to specific fixes. For the wider speed checklist, see our page speed optimization guide.
