If you've ever had someone audit your website, you may have heard terms like LCP, INP and CLS, followed by "your Core Web Vitals are failing." It sounds technical, but the idea is simple: Google wants to measure whether people actually enjoy using your site.
Here's what the three metrics mean in plain English, why they matter for your business, and what to do if your site falls short.
What are Core Web Vitals?
Core Web Vitals are three metrics Google uses to measure real-world user experience on a web page. Each one answers a question every visitor asks without thinking about it:
- Does the page show up quickly? That's LCP.
- Does it respond when I tap? That's INP.
- Does the content stay put, or jump around? That's CLS.
What makes them different is that they're measured from real users, not just testing tools. According to web.dev, a page passes when at least 75% of visits meet the "good" threshold for all three.
LCP: how fast does the main content appear?
Largest Contentful Paint measures how long it takes for the biggest piece of content in the first screen to show up, usually a hero image, a product photo or a large heading.
- Good: 2.5 seconds or less
- Needs improvement: 2.5 to 4 seconds
- Poor: over 4 seconds
Think of walking into a shop where the lights take ages to come on. You're inside, but there's nothing to look at yet.
Common causes: heavy hero images, a slow server, and fonts or scripts that block the page from rendering.
INP: how responsive is the page?
Interaction to Next Paint measures the delay between a tap, click or key press and the moment the screen visibly responds. Think "Add to cart", opening a menu or picking a product colour.
- Good: 200 milliseconds or less
- Needs improvement: 200 to 500 milliseconds
- Poor: over 500 milliseconds
INP replaced the older FID metric in March 2024. It's stricter, because it looks at interactions throughout the whole visit, not just the first one.
A button that takes half a second to react feels broken. People tap again, get frustrated, and sometimes leave.
Common causes: too much JavaScript running at once, heavy third-party scripts and plugins, and complex animations.
CLS: does the layout jump around?
Cumulative Layout Shift measures how much elements move unexpectedly while the page loads. You know the feeling: you go to tap a link, an image or banner pops in above it, everything shifts down and you tap the wrong thing.
- Good: 0.1 or less
- Needs improvement: 0.1 to 0.25
- Poor: over 0.25
CLS isn't measured in seconds. It's a score reflecting how much of the screen shifted, and by how far.
Common causes: images and videos without set dimensions, banners or notices injected at the top after loading, and web fonts that change size when they load.
Do Core Web Vitals affect SEO?
Yes, but don't overstate it. Google Search Central says Core Web Vitals are used by its ranking systems as part of page experience, while also making clear that relevant, helpful content matters most.
So a lightning-fast page with thin content won't magically rank. But between two pages with similar content, the one with the better experience has an advantage.
The bigger reason to care is commercial: visitors stay longer, mis-tap less and contact you more often.
How to check your own site
Two free tools cover it:
- PageSpeed Insights: paste a URL into pagespeed.web.dev to test a single page. If your site has enough traffic, you'll see real-user data.
- Google Search Console: the Core Web Vitals report groups your pages into good, needs improvement and poor, for mobile and desktop.
Our guide on how to check your website speed in 10 minutes walks you through the test step by step.
What to do if your site fails
A sensible order of attack:
- Fix the pages that matter first: homepage, best-selling products, landing pages you're paying to send traffic to.
- Start with LCP: optimizing the hero image and server response usually brings the biggest win.
- Cut unused code: remove plugins and scripts you don't need to improve INP.
- Reserve space for images and banners: set dimensions so the layout doesn't jump, bringing CLS down.
Real-user data covers the last 28 days, so allow a few weeks after a fix for reports to catch up.
If the site is built on a very heavy platform, patching it piece by piece can cost more than rebuilding it lean. That's worth discussing with someone who knows the trade-offs.
The bottom line
Core Web Vitals aren't a vanity score. They're Google's way of measuring what customers feel: is the page fast, smooth and stable?
Bina builds with Core Web Vitals in mind from the design stage and checks them again before handover, so you're not fixing things later. See how we work on our Services page, or send us your current site and we'll tell you where it stands.
