Core Web Vitals.

Core Web Vitals are three metrics that Google uses to evaluate the user experience on a website: Largest Contentful Paint (LCP) for the load time of the largest visible element, Interaction to Next Paint (INP) for responsiveness to clicks and input, and Cumulative Layout Shift (CLS) for visual stability. The evaluation is based on the experiences of real visitors. For your business, these metrics provide the most tangible answer to the question of whether your website is fast and stable enough on mobile devices.

How Core Web Vitals Work

According to web.dev, there are fixed thresholds for “good” and “bad” for each of the three metrics. LCP is considered good up to 2.5 seconds and bad above 4 seconds. INP is considered good up to 200 milliseconds and bad above 500 milliseconds. CLS is considered good up to 0.1 and bad above 0.25. Anything in between is considered in need of improvement.

According to web.dev, the 75th percentile is the key metric. A page is considered to meet the criteria if, for each of the three metrics, at least three out of four page views fall within the “good” range. Mobile and desktop are evaluated separately.

What Your Business Should Keep in Mind

First, look at the mobile metrics. Since mobile and desktop are evaluated separately, good desktop metrics don't tell you anything about mobile. Check both views and start with the one that's performing worse.

Don't confuse the score with the Core Web Vitals. The score in PageSpeed Insights is not the same as the three thresholds. Our article " How to Read PageSpeed Insights Correctly" explains why a number like 69 points doesn't tell the whole story and which value really matters.

Look for the bottleneck where the poor metric is occurring. A slow LCP is often caused by a large cover image or video at the very top of the page. A high CLS is often caused by banners, fonts, or images without fixed dimensions that shift the layout after the page has loaded. A slow INP indicates a large amount of script code, such as from extensions and embedded services.

Re-measure after every major change. A new cover photo, an additional plugin, or a different cookie banner can significantly affect the metrics. Keep track of when you made each change so you can identify the causes later.

Frequently Asked Questions About Core Web Vitals

What happened to FID? According to web.dev, INP replaced the former First Input Delay (FID) metric on March 12, 2024. Any guides that still refer to FID are outdated in this regard.

Is it enough for the homepage to have good metrics? No. Above all, check the pages where inquiries originate—that is, service pages and every landing page. Slow landing pages directly impact your conversion rate.

What does the 75th percentile mean? It means that three out of four runs must be at least as good as the threshold value. Therefore, a few quick measurements on your own computer are not sufficient proof.

The Speed Check will show you how your site performs across these three metrics. If the issues stem from deeper structural or technical problems, our web design team will help you resolve them.