Section 1
Three feelings, three numbers
Strip the acronyms and the metrics describe sensations you know from your own browsing. LCP, Largest Contentful Paint, is the moment the page's main content appears; before it, the buyer stares at a blank or half-drawn screen wondering if anything is coming. INP, Interaction to Next Paint, is how quickly the page visibly reacts when someone taps a button or opens a menu; sluggish response reads as broken. CLS, Cumulative Layout Shift, measures how much the page jumps around while loading, the effect that makes someone tap 'Book a call' and hit a cookie banner instead. Google's web.dev documentation defines good thresholds for each: 2.5 seconds, 200 milliseconds, and 0.1 respectively. Buyers never use these words. They just leave when the numbers are bad. To see how this connects to the wider system, read [The Technical Foundations of a Website That Sells: Speed, Accessibility, and Trust](/blog/technical-foundations-website-that-sells).
Section 2
The operator's scorecard
The table below is the entire technical vocabulary you need for a conversation with a developer or agency. Two details matter more than memorizing thresholds. First, these are field metrics: Google measures them from your actual visitors' devices via the Chrome User Experience Report, so your real-world score includes the buyer on an aging phone in a parking lot, not just your designer's MacBook. Second, the standard is the 75th percentile, three-quarters of visits must hit the threshold, per web.dev. That is why 'it loads fine for me' settles nothing. Check your true numbers free in ten minutes: PageSpeed Insights shows field data per page, and Google Search Console aggregates Core Web Vitals across your whole site under a dedicated report.
Section 3
Do vitals move rankings, revenue, or both?
Be precise about the claim, because vendors inflate it. Google confirms page experience, including Core Web Vitals, plays a role in ranking, but a modest one; great content outranks fast mediocrity. The stronger business case is direct: the same slowness and jank the metrics measure is what drives abandonment. Google's published case studies make the link concrete, Vodafone tied a 31% LCP improvement to 8% more sales, and Renault documented bounce rates falling and conversions rising as LCP improved. So treat the SEO benefit as a bonus and the conversion benefit as the prize. A useful mental model: Core Web Vitals are the first impression quantified. Improving them does not persuade anyone, it ensures your persuasion is delivered intact, to more of the people you already paid to reach. For a deeper look at this, see [Core Web Vitals in Business Terms: What a Slow Website Costs You](/blog/core-web-vitals-in-business-terms-what-a-slow-website-costs-you).
Section 4
What to actually do with red scores
Do not commission a redesign. Red vitals are usually a short list of mechanical fixes, and the order matters. Start with LCP, because it gates everything: compress the hero image, enable caching, and if the server is slow, move hosting, covered in the speed-economics and hosting articles in this series. Then CLS, often a one-day fix: set explicit dimensions on images and reserve space for any banners. INP is typically the stubborn one, rooted in theme and plugin bloat; sometimes the honest answer is a lighter rebuild of key pages. Inside ConvertOS, the web-design module of LeverageOS, we set a simple governance rule any operator can copy: the money pages, home, services, booking, must stay green, checked monthly, with one named owner. Vitals drift; ownership keeps them honest. A useful companion to this piece is [CRM for Small Service Teams: What You Actually Need (and What You Don't)](/blog/crm-for-small-service-teams).