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 part of Google's "Page Experience" signals.
Unlike traditional ranking factors (like keywords or backlinks), CWV looks at the technical performance of your site from the user's perspective. It doesn't care what your content says; it cares how it feels to load it.
The Three Pillars of Page Experience
LCP: Largest Contentful Paint
Definition: LCP measures how long it takes for the largest visible element (usually a hero image, video, or H1 block) to fully appear on the screen.
The User Feeling: "Is this meaningful?" If LCP is slow, the user stares at a blank white screen, wondering if the site is broken.
≤ 2.5s
≤ 4.0s
> 4.0s
INP: Interaction to Next Paint
Definition: INP measures the latency of every tap, click, and keyboard interaction throughout the entire lifespan of the page visit. It replaced FID (First Input Delay) in 2024.
The User Feeling: "Is this broken?" If you click "Add to Cart" and the page freezes for 500ms before responding, that is bad INP. It represents rage-clicks.
≤ 200ms
≤ 500ms
> 500ms
CLS: Cumulative Layout Shift
Definition: CLS measures how much elements move around on the page while it loads. It is a mathematical score calculated by (Impact Fraction × Distance Fraction).
The User Feeling: "Annoyance." We have all been there: You go to click a button, but an ad loads at the top, pushes the content down, and you click the wrong thing.
≤ 0.1
≤ 0.25
> 0.25
The CrUX Report: Field vs. Lab Data
One of the most confusing parts of CWV is why your "PageSpeed Insights" score might say 90/100, but Google Search Console says you are "Failing."
🧪 Lab Data (Lighthouse)
This is a simulation. It runs on your computer or the testing server right now. It assumes a specific internet speed and device.
Use for: Debugging code changes immediately.
🌍 Field Data (CrUX)
This is real user data collected by the Chrome User Experience Report (CrUX). It averages the experience of actual humans visiting your site over the last 28 days.
Use for: What actually affects your Ranking.
Important: Google ranks you based on Field Data (CrUX), not Lab Data. If real users have slow phones, your score will be low, even if your server is fast.
Why Should You Care?
- 🏆 Ranking Factor: While Content is king, Page Experience is the tie-breaker. In competitive niches, CWV can determine who gets the #1 spot.
- 📉 Bounce Rate: Google found that as page load time goes from 1s to 3s, the probability of bounce increases by 32%.
- 💰 Conversion Rate: Slow sites kill sales. If a user can't interact (INP) with your checkout button, they can't pay you.
Is Your Site Failing CWV?
Now that you understand the metrics, it's time to fix them. Our Technical SEO Guide provides the code snippets, image settings, and server configs to get all metrics into the "Green."