In the post about speed testing we promised to explain the three mysterious metrics with the odd names: LCP, CLS, INP. Here they are, jargon-free, through a metaphor that sticks.
Imagine your website is a restaurant, and the visitor is a diner walking in.
LCP: how fast the main dish arrives
Largest Contentful Paint measures how long until the page’s main element (usually the hero image or the big headline) appears on screen.
At the restaurant: the diner sat down. How long until the main course reaches the table? Five minutes - wonderful. Forty minutes - they get up and leave, no matter how good the food is.
Google’s target: under 2.5 seconds. Above 4 is considered poor. Which matches real behavior: past 3 seconds of blank screen, most mobile visitors abandon.
CLS: the table that doesn’t wobble
Cumulative Layout Shift measures how much the page “jumps” while loading. You know when you try to tap a button, and suddenly an image loads and pushes everything down, and you tapped an ad instead? That’s bad CLS.
At the restaurant: you sat down, lifted your glass, and someone bumps the table. Then again. Would you come back?
Target: under 0.1 (it’s a ratio, not seconds). Usual culprits: images without defined dimensions, banners injected late, and fonts swapping mid-read.
INP: the waiter who responds immediately
Interaction to Next Paint measures how fast the page reacts to your actions: you tapped a menu - how long until something moves on screen?
At the restaurant: you wave at the waiter, and he… keeps chatting on the phone. Three seconds later he turns around. The food may be excellent, but the place feels like it doesn’t care.
Target: under 200 milliseconds. The INP killer is usually JavaScript overload: dozens of plugin scripts, pixels and chats choking the browser.
Where do you see your numbers?
Go to pagespeed.web.dev and enter your address. At the top of the report is the “Core Web Vitals Assessment”: data from your real visitors over the last 28 days (if the site has enough traffic). Green = passing; orange/red = work to do.
The key point: these metrics were not invented to please Google. Google simply measured what annoys humans. A site passing all three is simply pleasant to use - and a comfortable customer buys more. On the sites we build, all three are green by default, because when the foundation is right you don’t need patches.
Bottom line
Core Web Vitals are three simple questions: did the dish arrive fast? is the table steady? is the waiter attentive? Google measures them on your real visitors and factors the answers into rankings. Check yourself on PageSpeed Insights - and if something is orange or red, you now know exactly what a professional means by “improving the metrics”.
Want a site whose three metrics are green from day one? That’s our standard - let’s talk ↗