Core Web Vitals are three measurements Google uses to judge how your website feels to real visitors: how quickly the main content loads (Largest Contentful Paint, or LCP), how quickly the page responds when someone taps or clicks (Interaction to Next Paint, or INP), and how much the layout jumps around while loading (Cumulative Layout Shift, or CLS). Google's "good" thresholds are an LCP of 2.5 seconds or less, an INP of 200 milliseconds or less, and a CLS of 0.1 or less.
They matter for two reasons. Google uses page experience signals, including Core Web Vitals, as part of how it ranks pages. And, more directly, a slow or jumpy website frustrates the people you want to turn into customers. This guide explains each metric in plain English and what you can do about it.
What are Core Web Vitals?
Google introduced Core Web Vitals to give website owners a consistent way to measure user experience. Rather than a vague idea of "fast", they focus on three moments that visitors actually notice:
- Does the page show me something useful quickly? That is LCP.
- When I tap a button, does anything happen? That is INP.
- Does the page stay still, or does it jump about as it loads? That is CLS.
Crucially, Google assesses these using data from real visits to your site, collected from Chrome users who have opted in, not just lab tests. For each metric, Google looks at the 75th percentile, which roughly means three out of four visits need to hit the "good" threshold for the page to pass.
Largest Contentful Paint (LCP): loading speed
LCP measures how long it takes for the largest visible element on the screen, usually a hero image or a big heading, to appear. It is a good stand-in for "when does the page look ready?"
- Good: 2.5 seconds or less
- Needs improvement: between 2.5 and 4 seconds
- Poor: more than 4 seconds
Common causes of slow LCP
- Large, uncompressed hero images
- Slow hosting or servers far from your visitors
- Heavy themes and page builders that load lots of code before showing content
- Too many plugins, fonts and third-party scripts
- Content that only appears after JavaScript has run
Interaction to Next Paint (INP): responsiveness
INP replaced an older metric called First Input Delay in March 2024. It measures how long the page takes to visibly respond after someone interacts with it, such as tapping a menu, opening an accordion or pressing a "Book now" button. It looks across the visit, not just the first tap.
- Good: 200 milliseconds or less
- Needs improvement: between 200 and 500 milliseconds
- Poor: more than 500 milliseconds
Common causes of poor INP
- Large amounts of JavaScript running on the page
- Chat widgets, tracking scripts and ad tags competing for the phone's processor
- Complex sliders, pop-ups and animations
- Page builders that add a lot of code for simple features
Poor INP is particularly noticeable on mid-range and older phones, which many of your customers will be using.
Cumulative Layout Shift (CLS): visual stability
CLS measures how much the content moves around unexpectedly while the page loads. You have probably experienced it: you go to tap a link and the page jumps, so you tap an advert or the wrong button instead.
- Good: 0.1 or less
- Needs improvement: between 0.1 and 0.25
- Poor: more than 0.25
Common causes of high CLS
- Images and videos without set dimensions
- Cookie banners or notices that push content down
- Web fonts that swap in and change the size of text
- Adverts, embeds or widgets that load late and take up space
Why Core Web Vitals matter for rankings
Google has been clear that Core Web Vitals are part of its page experience signals, which its ranking systems take into account. It has also been clear that relevance and helpful content come first: a fast page with poor content will not outrank a slower page that answers the search much better.
So the honest way to think about it is this. Core Web Vitals will not rescue a weak website, but when you are competing with other local businesses offering similar services, a faster, smoother site removes a disadvantage and can help tip things in your favour. Speed is part of the same picture as the rest of your SEO, which we cover in our local SEO checklist for Scottish businesses.
Why speed matters for enquiries
Rankings are only part of the story. The bigger, more immediate impact of speed is on what visitors do once they arrive.
Think about how people find a local business. They are often on a phone, maybe on mobile data, maybe comparing three or four options from the search results. If your page is blank for several seconds, the back button is right there. If the menu does not respond, or the "Call now" button jumps out from under their thumb, they get frustrated and try the next business.
A fast, stable site does the opposite. It looks professional, feels trustworthy and lets people get to your phone number, quote form or booking page with no friction. That is why we treat speed as a conversion issue as much as an SEO one. Our post on how to get more enquiries from your website covers other fixes that work alongside it.
How to check your Core Web Vitals
You do not need any technical tools to get started.
- PageSpeed Insights: enter your web address at Google's PageSpeed Insights. The top section shows real-visitor data where Google has enough of it, and the lower section shows a lab test with suggestions.
- Google Search Console: the Core Web Vitals report groups your pages into good, needs improvement and poor, based on real visits.
- Test on your own phone: load your site on mobile data, not office Wi-Fi, and see how it feels.
Small sites with fewer visitors may not have enough real-world data for Google to show field results. In that case, the lab test is a useful guide, but treat it as an estimate.
How to improve Core Web Vitals
The fixes depend on what is causing the problem, but the most common improvements are:
- Compress and resize images, and serve modern formats
- Set width and height on images and embeds so space is reserved
- Cut unnecessary plugins, scripts and widgets
- Use good hosting with a content delivery network
- Load fonts efficiently and limit how many you use
- Avoid heavy page builders for simple sites
Some platforms make this harder than others. Template sites with many plugins often need a lot of tuning to pass, and can slip back after updates. Hand-coded sites start from a much lighter base. We explain the trade-off in WordPress vs hand-coded websites.
Every website we build through our website design service is hand-coded, image-optimised and hosted on a global edge network through our managed hosting, so good Core Web Vitals are the starting point rather than an afterthought.
FAQs
What is a good Core Web Vitals score?
Google's good thresholds are LCP of 2.5 seconds or less, INP of 200 milliseconds or less and CLS of 0.1 or less, measured at the 75th percentile of real visits.
Do Core Web Vitals affect Google rankings?
Yes, as part of Google's page experience signals, but relevance and content quality matter more. A fast site helps most when you are competing closely with similar businesses.
Why is my PageSpeed score different every time I test?
Lab tests vary slightly between runs because of network and server conditions. Focus on the real-visitor data and on trends over time rather than one score.
Can you fix Core Web Vitals on my existing website?
Often, yes. We start with an audit to find the biggest causes, fix what we can on your current platform, and recommend a rebuild only if the platform itself is holding you back.
If your website feels slow or you are failing Core Web Vitals, get in touch with Flux Web Design. We will check your site and tell you plainly what is slowing it down.
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- Core Web Vitals