You’ve done it yourself. You tap a link on your phone, wait a second or two, and then just… close the tab. No conscious decision. Just a reflex.
The behaviour is well documented. Google and DoubleClick’s “The Need for Mobile Speed” study, published in September 2016, found that 53% of mobile visits were abandoned if a page took longer than three seconds to load. The number is a decade old now, but the pattern it describes is exactly what Core Web Vitals was designed to measure: whether your website actually works for real visitors, on real devices, in real conditions.
But this isn’t just a search engine story. A site that passes Core Web Vitals is faster, more stable, and easier to use. Visitors feel that difference, and it shows up in whether they stay, enquire, or buy.
What are Core Web Vitals?
Core Web Vitals are three specific measurements Google uses to assess the quality of experience on a website. They don’t measure how the site looks or whether the copy is good. They measure how it feels to use: how quickly it loads, how fast it responds to clicks, and whether the layout jumps around while you’re reading.
What sets Core Web Vitals apart from older speed scores is that they’re based on data from real Chrome users, not simulated lab tests. Google collects anonymised performance data through the Chrome User Experience Report (CrUX) and evaluates your site against the 75th percentile of that data. That means 75% of your visitors’ actual experiences are what counts — not just the best or worst cases.
Google introduced the framework in May 2020, though it only began affecting rankings with the page experience update that rolled out during 2021. The most recent change came in March 2024, when one of the three metrics was replaced with a more accurate measure of interactivity.
The three metrics — what do they actually measure?
LCP — how quickly does the main content load?
LCP, or Largest Contentful Paint, measures how long it takes for the largest visible element on the page to finish rendering. That’s usually your hero image, main headline, or a product photo — whatever the visitor is actually waiting to see.
Google’s threshold for a good LCP score is 2.5 seconds. Over 4 seconds is classified as poor.
It’s the metric most sites fail. HTTP Archive’s Web Almanac 2025, drawing on CrUX data from July 2025, found that 62% of mobile pages achieve a good LCP — the lowest of the three metrics, and the main reason only 48% of mobile origins pass all three at once. One of the most common causes is a slow server response from the very start: when the server takes a little too long to send the first byte, the entire time budget is eaten up before the image has even started downloading. (There’s a reason first impressions happen so fast. If you want to understand what those first milliseconds do to a visitor’s judgement, the article Say It All in 50 Milliseconds covers it well.)
INP — does the page respond when you click?
INP, or Interaction to Next Paint, measures how quickly the page reacts visually when you click, tap, or type something. A menu item, a form field, a button — anything that’s supposed to do something when you interact with it.
The threshold for a good INP score is 200 milliseconds. Over 500 milliseconds is poor.
This metric replaced the older FID (First Input Delay) on 12 March 2024. FID only measured your very first interaction with a page, and Google’s reasoning for the switch was that it failed to capture how interactivity is actually experienced. INP measures every interaction across the entire visit and reports a value representative of the worst experiences, which is a considerably tougher assessment.
At its core, INP is a JavaScript problem. Heavy scripts, third-party widgets, and a page trying to do too much at once all make clicks feel sluggish or delayed.
CLS — does the layout jump around?
CLS, or Cumulative Layout Shift, measures how much the page content moves unexpectedly while you’re reading it. Images that pop in and push the text down. A cookie banner that appears and shifts everything. An ad that loads last and knocks the button you were about to tap off the screen.
The threshold for a good CLS score is 0.10. Over 0.25 is poor.
It’s easy to miss in testing because it’s most noticeable on slower connections and older devices — which is exactly where a lot of your visitors are. The most common cause is images shipped without defined width and height attributes. When the browser doesn’t know how big an image is, it doesn’t reserve space for it. When the image loads, everything around it shifts.
Why does Google care about this?
Core Web Vitals are a confirmed ranking signal. Google has said so directly. Their Search Central documentation on page experience, last updated in December 2025, states plainly: “Core Web Vitals are used by our ranking systems.”
That doesn’t mean they’re the deciding factor between page one and page three. The same documentation makes clear there is no single page experience signal, and that “Google Search always seeks to show the most relevant content, even if the page experience is sub-par.” Relevance and content quality carry more weight. But Core Web Vitals are part of the picture, and they’re measured against real visitor data from your actual site.
The stronger argument for taking them seriously isn’t ranking — it’s business impact. In 2020 Deloitte ran “Milliseconds Make Millions”, a study commissioned by Google, covering 30 million user sessions across 37 brands in Europe and the US over a four-week period. A 0.1-second improvement in load time increased retail conversion rates by 8.4% and average order value by 9.2%. In lead generation, progression from the first step of a form through to submission rose by 21.6%.
It’s not the search engine that loses when your site is slow. It’s you.
What do Core Web Vitals have to do with AI search?
A lot of businesses are thinking about AI search right now — whether they show up in ChatGPT answers, or get cited in Google’s AI Overviews. Core Web Vitals play a role here, but not in the way most people expect.
The connection runs through ordinary search. Google’s documentation on AI features states that to be eligible as a supporting link in AI Overviews or AI Mode, a page must be indexed and eligible to appear in Google Search with a snippet — and that there are no additional requirements beyond that. Being visible in regular search is the prerequisite. Ahrefs’ analysis of 1.9 million citations across one million AI Overviews, published in July 2025, found that just over 76% of cited pages ranked in the top ten organic results. So Core Web Vitals feed into AI visibility indirectly, through ranking.
Whether there’s a direct connection has actually been tested. Dan Taylor of SALT.agency examined 107,352 pages cited in Google’s AI Overviews and AI Mode and published the results in Search Engine Land in January 2026. The correlations were weak — between −0.12 and −0.18 for LCP, and between −0.05 and −0.09 for CLS — and were driven almost entirely by extreme outliers. The conclusion is worth keeping: if your scores are already in the acceptable range, improving them further gives no measurable edge in AI search, while genuinely bad scores can be a real barrier. Core Web Vitals act as a floor, not a lever.
WordPress and Core Web Vitals — a known challenge
A lot of business websites are built on WordPress, and WordPress is among the platforms that struggle most to pass all three metrics. An analysis of CrUX data from January to April 2026, published in Search Engine Journal in May 2026, found that around 49% of WordPress sites get a good Core Web Vitals score. The equivalent figures are 80% for Wix, 79% for Shopify and 85% for Duda. Drupal (64%) and Joomla (58%) also come out ahead.
That’s rarely WordPress’s fault in itself. It’s how the site was built.
Heavy page builders like Elementor and Divi load large amounts of code the page may not even need. Images that were never converted to modern formats burn through the LCP budget. Plugins that inject scripts on every page slow down interactivity. And hosting with a high server response time means the whole chain starts at a disadvantage.
None of these are unsolvable problems. They’re well-understood problems with well-understood fixes: better hosting, smart caching, image optimisation, and themes that don’t carry unnecessary code. But you need to know what you’re looking for. That’s exactly what we handle at Monprez when building and maintaining websites for businesses — read more about how we work with hosting, updates and maintenance.
How do you know how your site is performing?
The easiest starting point is Google PageSpeed Insights. Paste in your URL and the tool gives you both a lab score and, if enough data exists, real field data from actual visitors. It’s free and needs no login.
If you want to see the picture across your whole site rather than individual pages, the Core Web Vitals report in Google Search Console is more useful. It groups pages with similar performance together and shows where problems are systematic — for example, if all your blog posts or all your service pages are failing the same metric.
Neither tool requires a technical background to understand. Green is good, yellow needs work, red is a problem. Start there.
Common questions about Core Web Vitals
What counts as a good Core Web Vitals score?
Google classifies sites into three levels: good, needs improvement, and poor. The goal is to reach the green zone on all three metrics: LCP under 2.5 seconds, INP under 200 milliseconds, and CLS under 0.10. That assessment is made at the 75th percentile of your visitor data, separately for mobile and desktop.
Do Core Web Vitals affect my Google ranking?
Yes, but in a limited way. Google’s documentation confirms Core Web Vitals are used in its ranking systems, but also that there is no single page experience signal and that Search always seeks to show the most relevant content even where the page experience is sub-par. You can rank well with great content despite weak Core Web Vitals scores, and you can have perfect scores without ranking at all if your content doesn’t match what people are searching for.
Do I need to worry about Core Web Vitals if I have a small website?
Yes, but keep things in proportion. For a small site with limited traffic, Core Web Vitals rarely determine outcomes on their own. The priority is making sure you don’t have severe problems that are actively hurting the experience. Sites without enough traffic also won’t have enough CrUX data for the metrics to be based on real visitors at all.
Do Core Web Vitals affect AI search visibility in tools like ChatGPT and Perplexity?
Indirectly, yes. To be cited in Google’s AI Overviews a page must be indexed and eligible to appear in regular search, and according to Ahrefs just over three quarters of cited pages rank in the top ten organic results. For other AI tools like ChatGPT and Perplexity, there’s no confirmed direct connection to Core Web Vitals scores. What consistently matters most for AI citation is content quality, authority, and making sure your site is technically accessible to the crawlers that gather information.
Not sure where your site stands? We’re happy to take a look. Get in touch with Monprez and we’ll go through what could be improved for your specific site.