People don't wait. If your website takes more than three seconds to show something useful, a considerable share of your visitors have already left before seeing your offer. And Google knows it: speed has been a ranking factor for years. Core Web Vitals are how it measures that experience.
The good news is they can almost always be fixed. Let's look at what exactly they measure, how to check them on your site and what usually lies behind a slow load.
What Core Web Vitals are
They're three metrics Google uses to sum up whether your website feels fast and stable for a real person, not a robot. Each one measures a different moment of the experience.
LCP — Largest Contentful Paint
Measures how long the main element of the page takes to appear: usually the large header image or the headline. It's your 'first impression.' The goal is for it to happen in under 2.5 seconds. If your LCP drifts to five or six seconds, the visitor perceives the site as heavy even if it loads fine afterwards.
INP — Interaction to Next Paint
Measures how quickly your website responds when someone clicks, taps or types. A page can look loaded and still feel 'sluggish' if it's slow to react. The goal is to stay below 200 milliseconds. It usually gets worse when there's too much JavaScript running at once.
CLS — Cumulative Layout Shift
Measures how much the content moves while it loads. It's surely happened to you: you go to press a button, a banner drops in suddenly and you end up pressing something else. That's high CLS, and it's one of the most frustrating things. The goal is to keep it below 0.1.
How to measure your site in five minutes
- PageSpeed Insights: paste your URL and it gives you the three metrics with real user and lab data. It's free and it's the starting point.
- Search Console: in the 'Core Web Vitals' report you see how many of your URLs are green, amber or red, grouped by issue.
- The browser DevTools: the Lighthouse tab audits a page and gives you a prioritized list of what to fix.
A tip: always look at the mobile data. Most traffic comes from phones and that's where slow sites show most.
What usually lies behind a slow website
In 90% of cases, the culprits repeat:
- Unoptimized images. 4 MB photos that could weigh 200 KB. Compressing and serving in modern formats like WebP or AVIF is the fastest win there is.
- Too many third-party scripts. Every chat, tracking pixel and widget adds weight and blocks the load. It's worth auditing which ones truly add value.
- A heavy theme or template. Many templates load features you don't use. Sometimes what's left over weighs more than what you show.
- No caching or CDN. Serving the site from a single distant server makes every visitor pay for the trip. A CDN distributes the content close to each user.
- Badly loaded fonts. A font that blocks the render can delay everything else.
A fast website isn't a technical luxury: it's the difference between being read or having the tab closed.
Why this is money, not aesthetics
There's plenty of research linking speed to conversion: the longer a page takes, the more people leave and the fewer buy. On top of that comes the SEO effect. All else being equal, Google prefers to show the site that offers the better experience. Improving your Core Web Vitals works on both fronts at once: more visits and more conversion of those visits.
How we approach it
When we build a website we start from performance on day one, not as a patch at the end. Clean code, optimized images, well-configured caching and only the essential scripts. And if you already have a slow site, we run an audit and tell you exactly what's slowing it down and how much can be gained.
You can see how we handle web development and technical SEO, or take a look at real projects we've launched.