Website speed and Core Web Vitals: why a slow website costs you customers
Google measures your website's experience with three metrics: LCP, INP and CLS. What each one means, what the good values are and how to improve them on your site.
Try this right now: take out your phone, turn off wifi and open your website on mobile data. Count the seconds until you can read something. Now imagine you are a customer who arrived from an ad you paid for, with three of your competitors' tabs open next to it.
Would you wait? Most people would not. Speed is not a technical detail: it is part of your sales process.
What are Core Web Vitals?
They are the three metrics Google uses to measure a page's real experience: how fast it loads, how fast it responds and how stable it looks. According to Google Search Central, good values are:
| Metric | What it measures | Good value |
|---|---|---|
| LCP | How long the main content takes to appear | Less than 2.5 seconds |
| INP | How fast it responds to a click or tap | Less than 200 milliseconds |
| CLS | How much elements shift while loading | Less than 0.1 |
Google recommends achieving good Core Web Vitals to succeed in Search and deliver a good experience, because it aligns with what its ranking systems seek to reward. The full technical explanation of each metric is on web.dev.
Why does a slow website cost me sales?
Because every bad metric translates into a frustrated customer at a specific moment:
- High LCP: the customer sees an empty screen and leaves.
- High INP: they tap the WhatsApp button and nothing happens; they think the page is broken.
- High CLS: the button moves right when they are about to tap it and they end up somewhere else.
And it is not just Google: AI search engines also reward technically healthy sites, as we explain in what GEO is and how to appear in AI answers.
Common mistake: measuring the website from the office computer, on fiber, and concluding that “it loads fast”. Your customer opens it from a mid-range phone on mobile data. Always measure the mobile version.
How do I improve my site's Core Web Vitals?
- Images in modern formats (WebP or AVIF), with defined width and height so they do not jump. Improves LCP and CLS.
- Less JavaScript: every extra script delays the response to clicks. Improves INP.
- Lazy loading of what is further down the page. Improves LCP.
- Optimized fonts and styles so the content appears first.
- Good hosting with a CDN, serving the page from a location close to the visitor.
Often the underlying problem is the platform: a WordPress site loaded with plugins is hard to speed up. This very website moved to a static site for that reason, and we explain how to do it without losing rankings in migrating from WordPress to Cloudflare Pages without losing SEO.
How do I measure my website's speed?
With two free Google tools:
- Google Search Console, Core Web Vitals report, with data from your site's real users.
- PageSpeed Insights to review a single page and see what to fix.
Check first the pages that move the most money: the home page, the service pages and the pages your ads point to.
In short
A fast website keeps more visitors, converts more and is better aligned with what Google rewards. Watch three metrics (LCP, INP and CLS) and always measure them on mobile. Those seconds you counted at the start are customers who stay or leave. We build fast sites from the design stage in our web development service.
Frequently asked questions
Where can I see my site's Core Web Vitals?
In Google Search Console, in the Core Web Vitals report, with data from real users. For a single page you can use PageSpeed Insights.
Does speed affect rankings?
Google recommends achieving good Core Web Vitals because, together with other aspects of page experience, it aligns with what its ranking systems seek to reward.
What is LCP in simple words?
It is the time it takes for the page's main content to appear, usually the large image or the title. Good is less than 2.5 seconds.
Why is my website fast on my computer and slow on my phone?
Because the phone has less power and often a worse connection. That is why measurements should always be done on mobile.
Do not stop at the theory: apply it to your business
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