Core Web Vitals Simply Explained: LCP, INP and CLS for SMEs

When you start looking into the speed of your website, sooner or later you come across three cryptic abbreviations: LCP, INP and CLS. Together they're called Core Web Vitals, and Google uses them to measure how good a page feels for real visitors. That sounds like technical stuff for specialists, but it isn't. At heart, these three values are simply very human questions.

In this post I'll explain what the Core Web Vitals really mean, which values count as good and how to measure the three vitals yourself, with no prior knowledge and no expensive tool.

What are the Core Web Vitals anyway?

The Core Web Vitals are three metrics with which Google assesses the user experience of a website. They feed into the ranking, a page that feels good has an easier time with Google. Importantly: Google doesn't measure in a lab on a perfect connection, but on real visitors, on real phones, with real reception.

Each of the three values answers a different question: does it load quickly? Does it respond smoothly? Does it stay calm? Let's look at them one by one.

LCP, does it load fast enough?

LCP stands for "Largest Contentful Paint." Behind the clunky name hides a simple question: how long does it take until the largest visible content appears? Usually that's a large image or the main heading, which is exactly what a visitor uses to recognise that the page is "there."

As a rule of thumb: under 2.5 seconds is good, anything over 4 seconds is too slow. If your LCP is dragging, it's almost always down to images that are too heavy or a sluggish server that takes too long to respond at all.

INP, does the page respond smoothly?

INP means "Interaction to Next Paint" and measures responsiveness. When someone taps a button, opens a menu or selects something, how quickly does the page visibly respond? Everyone knows the feeling of tapping and nothing happening, and then pressing a second time in annoyance.

A good INP value is under 200 milliseconds. Poor values often arise when too much code is working in the background, typical of pages built with lots of plugins or heavy page builders. Incidentally, in 2024 INP replaced an older metric called FID, because it reflects a page's responsiveness more honestly.

CLS, does the layout stay calm?

CLS stands for "Cumulative Layout Shift" and describes something that has annoyed everyone at some point: content that suddenly jumps around while loading. You want to tap a link, at the last moment an image or an ad loads in and pushes everything down, and you land somewhere else. That's exactly what CLS measures.

Here the rule is: the smaller, the better, a value under 0.1 is good. The most common cause of shifting is images without a fixed size specification or elements loaded afterwards that only claim their space once the visitor is already reading.

How do I measure my Core Web Vitals?

The nice thing is: you need neither money nor technical knowledge for it. These tools are free and used within minutes:

• PageSpeed Insights: Enter your page's address, and you get all three vitals, once from lab data, once from real visitor data, if there's enough traffic.
• Google Search Console: Here there's a dedicated "Core Web Vitals" report that shows which of your pages Google rates as good, needing improvement or poor.
• Lighthouse: built directly into the Chrome browser, good for a quick check while working on the page.

A tip for context: don't be alarmed if the values look worse on your phone than on your computer. Google mainly assesses the mobile view, and that's exactly where the largest share of visits is decided today.

Do you need to worry about it?

You don't have to become a tech expert. But it's worth getting to know the three values once and briefly checking your own page. Because poor Core Web Vitals cost twice over: visitors bounce before they've even seen your offer, and Google ranks you further back. Both slow you down quietly, but noticeably.

Most problems can be fixed, and it's easiest when a page is built lean and clean from the start. That's exactly why I code by hand instead of stacking up heavy templates. If you'd like to know how your page performs, I'm happy to look at the values together with you: just get in touch via the contact form. And if you'd like to dig deeper, you'll find more posts around speed, SEO and websites for Swiss SMEs.