Google made Core Web Vitals an official ranking factor in 2021, and every year since it's become a stronger signal in search results. Yet most small business owners have no idea what these metrics are, let alone how to improve them.
This guide cuts through the jargon. By the end, you'll understand exactly what the three Core Web Vitals measure, what scores you're aiming for, and the practical steps to get there.
What Are Core Web Vitals?
Core Web Vitals are a set of specific factors that Google considers important to the overall user experience of a webpage. They measure real-world performance from the user's perspective — not just technical benchmarks.
There are three metrics:
LCP — Largest Contentful Paint
What it measures: How long it takes for the largest visible element on the page (usually a hero image or headline) to load and become visible.
Why it matters: It's the closest proxy for "when does the page feel loaded?" to a real user. A slow LCP means your visitor is staring at a blank or partial page.
| Score | LCP Time |
|---|---|
| Good | Under 2.5 seconds |
| Needs Improvement | 2.5 – 4.0 seconds |
| Poor | Over 4.0 seconds |
Common causes of poor LCP: Large unoptimised hero images, render-blocking JavaScript, slow server response times, no CDN.
INP — Interaction to Next Paint
What it measures: How quickly the page responds when a user interacts with it — clicking a button, tapping a menu, selecting an option.
Why it matters: A page that looks fast but feels laggy when you interact with it is a poor experience. INP replaced FID (First Input Delay) in March 2024 as it gives a more comprehensive picture of responsiveness.
| Score | INP Time |
|---|---|
| Good | Under 200ms |
| Needs Improvement | 200 – 500ms |
| Poor | Over 500ms |
Common causes of poor INP: Heavy JavaScript execution, third-party scripts (chat widgets, analytics, ad trackers), unoptimised event handlers.
CLS — Cumulative Layout Shift
What it measures: How much the page layout shifts unexpectedly while loading. You know the frustrating feeling when you're about to tap a button and the page jumps and you tap something else instead? That's a CLS problem.
Why it matters: Layout shifts cause mis-taps, lost reading position, and general frustration. They're often caused by images loading without defined dimensions or ads injecting into the page.
| Score | CLS Score |
|---|---|
| Good | Under 0.1 |
| Needs Improvement | 0.1 – 0.25 |
| Poor | Over 0.25 |
Common causes of poor CLS: Images without width/height attributes, fonts loading late and causing text reflow, dynamically injected banners or cookie notices.
How to Measure Your Core Web Vitals
The most reliable tools to check your scores:
- Google PageSpeed Insights (pagespeed.web.dev) — free, shows both lab and field data
- Google Search Console — the Core Web Vitals report shows real-user data across all your pages
- Chrome DevTools — the Performance and Lighthouse tabs give detailed breakdowns
- WebPageTest.org — advanced testing with waterfall charts and filmstrip view
Important: Always test on mobile, not just desktop. Google uses mobile-first indexing, so your mobile scores are the ones that affect ranking.
How to Improve Your LCP
- Convert hero images to WebP format and compress to under 150KB
- Add
loading="eager"andfetchpriority="high"to your hero image - Use a CDN (Content Delivery Network) to serve assets from servers closer to your users
- Upgrade to faster hosting — shared hosting often has slow Time to First Byte (TTFB)
- Remove render-blocking scripts by adding
deferorasyncattributes
How to Improve Your INP
- Audit and remove unused third-party scripts — every chat widget, pixel, and tag adds JS overhead
- Use a tag manager to load non-critical scripts after the page is interactive
- Break up long JavaScript tasks into smaller chunks using
setTimeoutorrequestIdleCallback - Consider removing or replacing heavy page builders that generate bloated JavaScript
How to Improve Your CLS
- Always define explicit
widthandheightattributes on every image and video - Reserve space for ads and embeds using CSS
min-height - Use
font-display: swapcarefully — it can cause text to shift when the web font loads - Preload key fonts using
<link rel="preload">in your document head - Avoid inserting content above existing content after the page has loaded
The Quick-Win Checklist
If you want to improve your scores without a full site rebuild, start here:
- Run PageSpeed Insights and note your current scores
- Compress all images and convert to WebP
- Add width/height to all images in your HTML
- Audit third-party scripts and remove anything non-essential
- Move to better hosting or add a CDN
- Re-test and track progress in Google Search Console
Most small business sites can achieve "Good" scores across all three metrics by addressing image optimisation and third-party script bloat alone. These two issues account for the majority of poor Core Web Vitals scores we see in audits.
Not sure where your site stands?
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