You've probably seen "Core Web Vitals" mentioned in an SEO report and nodded along without fully knowing what it meant. That's fair — the official explanations are written for engineers. Here's the version written for the person paying the invoice.
Core Web Vitals are three specific measurements Google uses to judge what it's actually like to use your website in the real world. They're not abstract technical scores — each one maps to something a visitor actually feels.
LCP — how long the important stuff takes to show up
Largest Contentful Paint measures how long it takes for the biggest visible thing on the page — usually a hero image or headline — to actually render.
This is the "is this page ever going to load" feeling. A visitor staring at a blank or half-loaded screen is a visitor deciding whether to wait or leave.
- Good: 2.5 seconds or under.
- Poor: over 4 seconds.
INP — how responsive the page feels once it's loaded
Interaction to Next Paint measures the delay between a visitor doing something — tapping a button, opening a menu, typing in a field — and the page actually responding. It replaced an older metric (First Input Delay) in 2024 because it measures responsiveness across the entire visit, not just the very first click.
This is the "why isn't this working" feeling — the tap that seems to do nothing for a beat too long, so the visitor taps again, or gives up.
- Good: 200 milliseconds or under.
- Poor: over 500 milliseconds.
CLS — whether the page holds still
Cumulative Layout Shift measures how much content unexpectedly jumps around as a page loads — an image popping in and shoving the text below it down, a late-loading banner pushing the button you were about to tap out from under your finger.
This is the "I clicked the wrong thing because the page moved" feeling. It's one of the more infuriating experiences on the web, and it's also one of the most common — usually from images or ads loading without a reserved space.
- Good: a score of 0.1 or under.
- Poor: over 0.25.
Why Google cares enough to make this a ranking factor
Because these three numbers correlate strongly with whether someone actually has a good experience on your site — and a search engine's whole job is sending people somewhere they'll actually be glad they went. Good Core Web Vitals won't single-handedly outrank a competitor with better content, but poor ones will hold you back regardless of how good everything else is.
How to check your own site
Go to Google PageSpeed Insights, enter your URL, and look at the mobile score first — it's almost always worse than desktop, and it's the one that counts most for ranking. You'll get real numbers for all three metrics, plus a list of what's specifically dragging each one down.
What usually causes the poor scores
- Poor LCP: Oversized images, slow hosting, render-blocking scripts — see the full breakdown in why your website is slow.
- Poor INP: Heavy JavaScript that keeps the browser too busy to respond immediately to input.
- Poor CLS: Images and embeds without reserved dimensions, fonts that swap in late and reflow text, content injected above existing content.
All three are fixable without a full rebuild in most cases — they're line items on a technical checklist, not a reason to start over. We cover the fuller list in our technical SEO checklist.
Want to know your actual numbers, not just the theory? We'll run the real audit on your strategy call.