The three metrics in plain words
Largest Contentful Paint (LCP) measures when the biggest visible element, usually a hero image or headline, finishes loading. Google treats 2.5 seconds or less as good. Interaction to Next Paint (INP) measures how long the page takes to respond after someone taps or clicks; 200 milliseconds or less is good. Cumulative Layout Shift (CLS) measures how much content moves unexpectedly; 0.1 or less is good.
INP replaced the older First Input Delay metric in 2024, which caught many sites off guard because it measures every interaction, not just the first.
How to check your site
Open PageSpeed Insights and enter your homepage and one important service page. The top section shows field data from real Chrome users when your site has enough traffic; the lower section shows a lab test. Field data is what Google uses. Google Search Console's Core Web Vitals report groups problem pages across the whole site.
The fixes that usually matter most
For LCP: serve images in modern formats at the size they are displayed, load the hero image with high priority and avoid hiding the main content behind a loading animation. For INP: cut heavy third-party scripts, chat widgets and tag managers that run on every click. For CLS: reserve space for images, ads and embeds, and load fonts so text does not reflow.
On our own site, moving a pinned scroll animation from JavaScript to CSS took the homepage layout shift from 1.45 to zero. Small structural choices often matter more than micro-optimizations.
Mobile first, always
Most business sites get the majority of their visits on phones, often on slower networks and older devices. Test with mobile throttling turned on. A page that feels instant on office Wi-Fi can take six seconds on a mid-range phone.
Make speed part of the build
Performance is cheapest when it is planned from the start: image pipelines, font loading, script budgets and server rendering. It is expensive to retrofit. That is why we review it before every launch as part of technical SEO, alongside the checks in our technical SEO checklist.