Core Web Vitals: what they are and why most websites fail them
Only 48 percent of mobile websites pass all three Core Web Vitals. Google uses these scores to help decide who ranks and who does not. If half the internet is failing, passing is a competitive advantage most businesses are leaving on the table.
Google is grading your website right now
Every time someone visits your website using Google Chrome, the browser quietly records how the page performed. How long the main content took to appear. Whether the layout shifted while things loaded. How quickly the page responded when they tapped a button.
That data feeds into the Chrome User Experience Report, a public dataset of real-world website performance. Not a lab simulation. Not a one-off test. Real visits from real people on real devices and real connections, collected continuously.
Google distils this data into three metrics called Core Web Vitals. These are the numbers that feed directly into your search rankings. They are also the numbers that determine whether your visitors have a smooth experience or a frustrating one.
The three metrics and where the lines are
Largest Contentful Paint measures how long it takes for the main content on your page to appear. The hero image. The headline. The thing the visitor came to see. Google considers anything under 2.5 seconds good. Between 2.5 and 4 seconds needs improvement. Over 4 seconds is poor.
Interaction to Next Paint measures how quickly the page responds when someone taps a button, clicks a link, or fills in a form. Under 200 milliseconds is good. Between 200 and 500 milliseconds needs improvement. Over 500 milliseconds is poor. This replaced the old First Input Delay metric in 2024 because Google wanted to measure responsiveness across an entire visit, not just the first click.
Cumulative Layout Shift measures how much the page moves around while it loads. You have experienced this. You start reading and the text jumps because an image loaded late. You tap a button and the page shifts so you hit the wrong link. Under 0.1 is good. Over 0.25 is poor.
These are not suggestions. They are the thresholds Google defined and uses when assessing your website.
The 75th percentile rule
Google does not use your best visit or your average. It uses the 75th percentile. That means 75 percent of all visits to your page must meet the "good" threshold for each metric. One fast load on your office desktop with fibre broadband does not offset a hundred slow loads on phones over 4G.
This is why testing your own website on your own computer tells you almost nothing useful. Your experience is not your customer's experience. Google measures real visits from real people, weighted towards the slower end, because that is the experience most of your visitors actually have.
Most websites fail
According to the HTTP Archive's 2025 Web Almanac, only 48 percent of mobile websites pass all three Core Web Vitals. Desktop fares better at 56 percent, but mobile is where Google looks first.
The hardest metric to pass is LCP. Only 68.6 percent of websites achieve a good loading score. CLS sits at 81.3 percent and INP at 86.6 percent. But you need to pass all three. Failing one is enough to fail the whole assessment.
The numbers get worse by industry. Only 39 percent of e-commerce websites pass all three, dragged down by image-heavy product pages and third-party scripts. The average B2B website has a mobile LCP of 7.05 seconds. That is nearly three times the 2.5-second threshold.
What failing actually costs
Core Web Vitals became an official ranking factor in 2021. As of Google's March 2026 core update, they are part of a composite performance score that sits alongside content signals in search rankings.
That does not mean a fast website with thin content will outrank a slow one with great content. It means that when content quality is comparable, the faster site wins. For local businesses competing against a handful of similar companies in the same area, content quality is often comparable. The technical edge becomes the tiebreaker.
Google's own research shows that 53 percent of mobile visitors abandon a site that takes longer than three seconds to load. A Deloitte study found that a 0.1-second improvement in load time can increase conversions by up to 10 percent. Not 10 percent faster. 10 percent more conversions.
Your LCP score is not a technical detail. It is the moment your visitor decides whether your website is worth waiting for.
The bar is not as high as you think
Half the internet is failing these tests. That sounds like a demanding standard. It is not. The thresholds are generous. An LCP of 2.5 seconds is not blazing fast. An INP of 200 milliseconds is not instant. A CLS of 0.1 allows for minor layout shifts.
A properly built website served from an edge network passes all three with room to spare. LCP under one second. INP under 50 milliseconds. CLS of zero. These are not aspirational targets. They are the natural result of building without heavy templates, plugin chains, and bloated JavaScript frameworks.
If your website runs on a CMS with a dozen plugins and shared hosting, these targets feel impossible. If it is built properly from the ground up, they are the default.
The bottom line
Core Web Vitals are the three metrics Google uses to judge how your website performs for real visitors on real devices. More than half of all mobile websites fail at least one. Most small business owners have never checked.
Passing all three puts you ahead of the majority. Not because the bar is high, but because most websites are built with tools that make passing difficult. A well-built site passes without effort. A poorly built one cannot be patched into compliance.
Check your scores at pagespeed.web.dev. Run the mobile test. Look at the Core Web Vitals section. If the numbers are red, your visitors already know.
How we can help
Every website we build passes all three Core Web Vitals on real-world mobile connections. Sub-second LCP. Zero layout shift. Instant interaction response. Not because we optimise after the fact, but because the architecture makes poor performance impossible.
We build static-first sites served from edge networks, with optimised images, local fonts, and no unnecessary JavaScript. The result is a website that loads faster than the vast majority of the internet and gives Google no technical reason to rank your competitors above you.