Google can measure how your site feels to a real person, and it has decided that matters for ranking. Core Web Vitals are the three numbers it uses to do it. They put a measurable score on the things visitors actually experience: how fast the main content shows up, how quickly the page responds when they tap or click, and whether the layout jumps around while it loads. If you’ve ever rage-tapped a button that wouldn’t respond, or had a page shove the content down just as you went to click, you’ve felt a failing Core Web Vital.
The three metrics that matter
Core Web Vitals are a subset of Google’s broader Web Vitals program, and they’re the three Google currently treats as essential. Each one has a clearly defined “good” threshold, measured at the 75th percentile of real visits — meaning at least three-quarters of your visitors need to clear the bar.
- Largest Contentful Paint (LCP) — loading performance. It marks when the biggest visible element (usually a hero image or headline block) finishes rendering. Good is 2.5 seconds or faster.
- Interaction to Next Paint (INP) — responsiveness. It measures how quickly the page visually responds to a user’s interactions across the whole visit, not just the first one. Good is 200 milliseconds or less.
- Cumulative Layout Shift (CLS) — visual stability. It captures how much the page unexpectedly jumps around as it loads. Good is a score of 0.1 or lower.
INP replaced FID — and it’s a tougher test
This is the update most outdated guides get wrong, so it’s worth being exact. The original responsiveness metric was First Input Delay (FID), which only measured the delay before the browser began processing your very first interaction. In March 2024, Google retired FID and replaced it with Interaction to Next Paint (INP) as an official Core Web Vital.
The change matters in practice. INP looks at all interactions during a visit, not just the first, and it measures the full time until the page actually paints a visual response — not just the initial delay. From our agency experience, plenty of sites that looked fine under FID quietly failed once INP went live, because their problem was never the first tap; it was sluggish response on every tap after. If your performance reports still reference FID, they’re measuring a metric that no longer exists.
Why this affects your traffic
Core Web Vitals are part of Google’s page experience signals, which feed into ranking. They aren’t a magic lever — Google has been clear that relevant, helpful content still wins, and great vitals won’t rescue a thin page. But when two pages are closely matched on relevance, experience can be the tiebreaker. What we consistently see working with clients is that the bigger payoff often isn’t the ranking nudge at all; it’s conversion. Faster, more stable pages keep more people from bouncing, and that shows up in revenue regardless of where you sit in the results.
How to measure them properly
There’s a trap here worth flagging. Tools split into two camps, and they don’t always agree:
- Field data (real users) — the Chrome User Experience Report (CrUX) and Google Search Console’s Core Web Vitals report show how actual visitors experienced your site. This is what Google uses for ranking.
- Lab data (simulated) — Lighthouse and the lab side of PageSpeed Insights run a single controlled test. Useful for debugging, but note that INP can’t be fully captured in a lab run because it depends on real interactions.
When we audit a site for clients, we always lead with field data from Search Console. A page can score beautifully in a clean lab test and still fail for real users on mid-range phones and slower networks. Optimize for the people, not the simulation.
What to fix first
Each metric has its usual suspects:
- To improve LCP: serve properly sized and compressed images, preload the hero element, cut render-blocking CSS and JavaScript, and put a fast host or CDN behind the site.
- To improve INP: break up long JavaScript tasks, defer or remove non-essential third-party scripts, and avoid heavy work on the main thread when a user interacts. Bloated tag managers and chat widgets are frequent culprits.
- To improve CLS: set explicit width and height (or aspect-ratio) on images and embeds, reserve space for ads and banners, and avoid injecting content above what the user is already reading.
Frequently asked questions
What are the three Core Web Vitals right now?
Largest Contentful Paint (LCP) for loading, Interaction to Next Paint (INP) for responsiveness, and Cumulative Layout Shift (CLS) for visual stability. INP replaced First Input Delay in March 2024.
What are the “good” thresholds?
LCP of 2.5 seconds or faster, INP of 200 milliseconds or less, and CLS of 0.1 or lower — each measured at the 75th percentile of real visits.
Will good Core Web Vitals boost my rankings?
They’re a real but modest ranking input and work best as a tiebreaker between comparable pages. They won’t outrank genuinely better, more relevant content, so treat them as a complement to strong content rather than a substitute.
Which tool should I trust?
For ranking purposes, the field data in Google Search Console and CrUX, because that reflects real users. Use Lighthouse and PageSpeed Insights to diagnose why a metric is failing, then verify the fix against field data over time.
Related terms
- Largest Contentful Paint (LCP) — the loading-speed vital; when your main content becomes visible.
- Interaction to Next Paint (INP) — the responsiveness vital that replaced FID in 2024.
- Cumulative Layout Shift (CLS) — the visual-stability vital that penalizes layout jumps.
- Page experience — Google’s broader signal set that Core Web Vitals feed into.
- Organic traffic — the search visits these metrics can help protect and grow.
- Mobile responsiveness — closely tied to vitals, since most failing scores show up on mobile devices first.
