What is a Core Web Vital?
Core Web Vitals are Google's standard measures of page experience, covering how quickly the main content appears, how responsive the page is to a tap, and whether the layout jumps around while loading. Core Web Vitals are measured on real visits from real devices, not only in laboratory tests — which is why a site can score well in a testing tool and still be reported as poor.
The short definition
Core Web Vitals are Google's standard measures of page experience, focused on loading, interactivity and visual stability.
They are measured on real visits from real devices, not only in laboratory tests — which is why a site can score well in a testing tool and still be reported as poor.
The three measures
Largest Contentful Paint (LCP). How long until the main content is visible. Usually driven by images, server response time and render-blocking resources.
Interaction to Next Paint (INP). How quickly the page responds when someone taps or clicks. Driven mostly by JavaScript doing too much. This replaced the older First Input Delay measure.
Cumulative Layout Shift (CLS). How much the page moves around while loading — the effect where you go to tap a button and an advert loads above it, shifting everything down. Usually caused by images and embeds without reserved space.
Why they matter beyond ranking
The ranking effect is real but modest — good content on a slow page still outranks poor content on a fast one.
The larger effect is on behaviour. A visitor on a phone, on mobile data, outside a job, will leave a slow page. Those departures never appear in your enquiry numbers, so the cost is invisible and continuous.
CLS in particular causes a specific failure: people mistap. On a service business site, that can mean tapping the wrong thing instead of the call button.
What usually causes poor scores on small business sites
- Oversized images. Photos uploaded at full phone resolution. The most common cause and the cheapest fix.
- Too many third-party scripts. Chat widgets, review carousels, tracking, fonts.
- Cheap shared hosting. Slow server response before your page even begins.
- Heavy page builders. Enormous markup for a simple page.
- Unreserved space for images and embeds, causing layout shift.
How to check
Google Search Console reports Core Web Vitals from real visits. PageSpeed Insights tests a single page and shows both lab and real-user data where available.
Test on a phone, not a desktop. Your customers are on phones.
What to do about it
Fix the biggest cause first, which for most small business sites is images. Then scripts. Then hosting. Rebuilding is sometimes cheaper than optimising, particularly on a heavy page builder.
Checking yours
Run your homepage and your busiest service page through PageSpeed Insights on mobile. The top recommendation is usually the right place to start.
Frequently asked questions
What are the three Core Web Vitals?
Largest Contentful Paint, how long until the main content appears; Interaction to Next Paint, how quickly the page responds to a tap; and Cumulative Layout Shift, how much the page moves while loading.
How much do they affect rankings?
Real but modest — good content on a slow page still outranks poor content on a fast one. The larger cost is visitors leaving before the page loads, which never appears in your enquiry numbers.
What causes poor scores on small business sites?
Oversized images most often, then third-party scripts like chat widgets and review carousels, then cheap shared hosting, then heavy page builders.
How do I check my scores?
Google Search Console reports them from real visits. PageSpeed Insights tests individual pages. Test on mobile, because that is where your customers are.