Core Web Vitals are metrics defined by Google to measure some fundamental aspects of real users’ experience on a web page: loading speed, responsiveness and visual stability.
They are not the only factor that determines rankings on Google, but they are part of the signals related to page experience. Above all, they are useful because they help you understand whether a site is genuinely fast and pleasant to use, not just “technically working”.
Which are the Core Web Vitals today?
The three main metrics are:
- LCP (Largest Contentful Paint): measures how quickly the main content of the page is displayed. A good value is within 2.5 seconds.
- INP (Interaction to Next Paint): measures how quickly the page responds to user interactions such as clicks, taps or keyboard input. A good value is 200 milliseconds or less.
- CLS (Cumulative Layout Shift): measures unexpected shifts of elements while the page loads. A good value is 0.1 or less.
To assess a page, Google looks in particular at the 75th percentile of real visits: in practice, most users need a good experience, not just those on a fast device or a perfect connection.
FID is no longer a Core Web Vital
Older articles about Web Vitals often mention FID (First Input Delay). In 2024 it was replaced by INP, which measures the page’s responsiveness more completely across the whole visit, not just the first interaction.
Why do Core Web Vitals matter?
A site with good Core Web Vitals tends to offer a smoother experience: the main content appears quickly, buttons respond without delay and the layout doesn’t “jump” while the user is reading or trying to click something.
This can have concrete effects on:
- user experience, especially on mobile;
- conversions, because less friction means fewer drop-offs;
- SEO, because Google considers Core Web Vitals within its ranking systems;
- the site’s overall technical quality.
This doesn’t mean a perfect score automatically guarantees the top spot on Google. Content, relevance, authority, structure and many other signals remain fundamental.
How to measure Core Web Vitals
The most useful tools are:
- PageSpeed Insights, which shows both real-user data when available and lab analysis;
- Google Search Console, useful for spotting groups of URLs with issues;
- Lighthouse, useful during development and debugging;
- Chrome DevTools, to analyze loading, scripts and layout shifts in more detail.
Real-user data and lab tests are not the same thing
It’s important to distinguish field data, collected from real users, from lab data, generated by a single simulation.
That’s why PageSpeed may show a very good Lighthouse test while real Core Web Vitals are still poor, or the opposite. The two kinds of data serve different purposes: real-user data tells you what users experience, lab data helps you diagnose the problem.
How to improve LCP
When LCP is high, the problem almost always lies in how the main content loads. Common causes are:
- heavy hero images;
- a slow server or high TTFB;
- render-blocking CSS and JavaScript;
- poorly loaded fonts;
- too many plugins or external resources.
The fix isn’t necessarily installing yet another caching plugin. First you need to understand which resource is really slowing the page down. I cover this approach in the guide on how to tell whether a WordPress site is really slow.
How to improve INP
A high INP means the page reacts slowly when the user interacts with it. The cause is often JavaScript keeping the browser busy for too long.
- cut unnecessary scripts and plugins;
- avoid complex widgets loaded on every page;
- break up long JavaScript tasks;
- limit trackers, chats, popups and third-party scripts when they aren’t essential.
How to improve CLS
CLS gets worse when elements move during loading. This often happens when images, banners or fonts load without the browser knowing in advance how much space to reserve.
- set image width and height;
- reserve space for banners, embeds and dynamic content;
- handle web fonts properly;
- avoid inserting elements above content that is already visible after loading.
Core Web Vitals and WordPress
On WordPress the most common causes are inefficiently loaded page builders, plugins that add CSS and JavaScript everywhere, unoptimized images, under-sized hosting and inconsistent caching setups.
Before making changes, it’s worth running an audit to understand which metric is off and why. To learn more, see my page on WordPress performance and optimization.
Conclusion
Core Web Vitals are useful because they turn generic ideas like “a fast site” or “a good user experience” into concrete metrics. Their value isn’t in chasing a 100/100, but in understanding where users run into slowdowns, delays or instability.
If your site has values outside the thresholds and it’s not clear where to start, let’s talk about the project: I can analyze the problem and identify the changes that will actually help.