If you have ever run your website through PageSpeed Insights, you have seen three strange abbreviations: LCP, INP and CLS. These are Google’s Core Web Vitals — measurements of how fast, responsive and stable your pages feel to real visitors.
Here is what they mean in plain English.
LCP — Largest Contentful Paint (loading)
What it measures: how long it takes for the biggest visible element — usually the hero image or main heading — to appear.
Good score: 2.5 seconds or less.
Common causes of a poor score: slow hosting, a huge uncompressed hero image, render-blocking CSS and JavaScript, or a heavy slider at the top of the page.
INP — Interaction to Next Paint (responsiveness)
What it measures: how quickly the page responds when someone taps a button, opens a menu or types in a form. INP replaced the older FID metric in 2024.
Good score: 200 milliseconds or less.
Common causes of a poor score: too much JavaScript, heavy page-builder add-ons, chat widgets and third-party scripts competing for the browser’s attention.
CLS — Cumulative Layout Shift (visual stability)
What it measures: how much the page jumps around while it loads — like when you go to tap a button and an image loads above it, pushing everything down.
Good score: 0.1 or less.
Common causes of a poor score: images without set dimensions, ads or embeds without reserved space, late-loading fonts, and banners that appear at the top after the page loads.
Lab data vs. field data
PageSpeed Insights shows two kinds of results:
- Field data — measurements from real Chrome users visiting your site over time. This is what Google uses.
- Lab data — a simulated test run right now. Useful for debugging, but it can differ from real-world results.
Google’s Search Console also has a Core Web Vitals report that groups your pages by status.
Do Core Web Vitals affect rankings?
They are part of Google’s page experience signals. Great content still matters most, but when competing pages are similar, a faster, smoother experience helps — and it definitely helps conversions, because people don’t wait for slow pages.
How to improve your scores
The fixes are usually practical, not magical: better hosting, caching, optimised images, less JavaScript and a cleaner page structure. I covered them in detail here: 12 fixes for a slow WordPress site.
Get your site checked
Request a free website audit and I will tell you how your key pages score and which fixes will make the biggest difference.
