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Core Web Vitals are three measurements Google uses to score the loading experience of your website: does the main content appear quickly, does the page respond straight away when someone taps it, and does the layout stay still instead of jumping around. Poor scores hit revenue in two ways: you rank lower on Google, and visitors leave before they buy.
You don't need to know how to fix them. But it pays to understand them well enough to tell whether your site is healthy, and to make sure your developer can't brush the question off.
The three measurements, in plain English
Picture a customer walking into a shop. Core Web Vitals measure exactly those first three moments:
- LCP: does the main content show up fast? (Largest Contentful Paint). Think of the time between a customer pushing the door open and actually seeing the shelves. Google treats under 2.5 seconds as good.
- INP: does it react when you tap? (Interaction to Next Paint). Like asking a shop assistant a question: do they answer right away, or just stand there? Under 200 milliseconds is good.
- CLS: does the layout stay put? (Cumulative Layout Shift). You go to tap "Buy", an image loads above it, the button jumps down, and you hit the wrong thing. Under 0.1 is good.
Google takes these numbers from real people visiting your site, not from a lab test. Definitions and thresholds: web.dev, Core Web Vitals.
Why it costs you money
This is the part many site owners underestimate. "What's a second or two?" Quite a lot, as it turns out.
- 53% of mobile visitors leave if a page takes longer than 3 seconds to load (source). Roughly one in two phone visitors is gone before they see what you sell.
- Conversion rates drop by about 4.42% on average for every extra second of load time (in the 0 to 5 second range), according to the same source.
- A page that loads in 1 second converts around 3 times better than one that loads in 5.
And that's only the visitors you lose after they arrive. There's a second layer: Google uses Core Web Vitals as a ranking signal. A slow site doesn't just lose the people who came in. It gets pushed further down the results, so fewer people arrive in the first place. You lose twice.
A slow website isn't a cosmetic technical issue. It's a revenue leak that runs around the clock: it loses the visitors you already have and shrinks the stream of new ones coming from Google.
How to check your own site in two minutes
You don't need a paid tool. Google gives you one for free:
- Open PageSpeed Insights.
- Paste in your website address and run the analysis.
- Look at two things: the overall score (green is good, orange or red needs work) and the panel showing LCP, INP and CLS.
- Check the "Mobile" tab as well as Desktop. Most of your visitors are probably on phones, and mobile scores are usually much lower than desktop.
Questions to ask your developer
If the scores are poor, don't accept "every site is like that". Ask directly:
- "What are the mobile Core Web Vitals for the homepage and our main product or service pages right now?"
- "Which of LCP, INP and CLS is failing, and what's the plan to fix it?"
- "Are you measuring with real-user data, or just running a one-off test on your own machine?"
A serious developer can answer these on the spot, with numbers. If the answers are vague, take note.
Next step
In short: Core Web Vitals are a health report for your website's speed, and poor scores cost real money, both in visitors who leave and in Google rankings. The good news is that they can be measured, and they can be fixed.
If you've just checked and found orange or red, that's exactly the kind of problem my SEO and performance work deals with every day: making sites load fast, stay stable and climb the rankings. Want a second opinion on your scores? Get in touch.
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