Core Web Vitals optimization means making technical changes to your site so it passes Google's three performance benchmarks: Largest Contentful Paint under 2.5 seconds, Interaction to Next Paint under 200 milliseconds, and Cumulative Layout Shift under 0.1. These metrics measure loading speed, interactivity, and visual stability. Google uses them as ranking signals, and sites that fail them often see lower positions in competitive SERPs, especially on mobile. LCP measures how fast your largest above-the-fold content element loads. Common fixes include upgrading hosting to reduce server response time below 600ms, implementing a CDN for static assets, preloading hero images, and compressing images to WebP or AVIF formats. If your LCP is a background image loaded via CSS, switching to an optimized image tag with fetchpriority='high' often cuts load time by 30-40%. INP replaced First Input Delay in March 2024 and measures responsiveness throughout the entire page session, not just initial load. Heavy JavaScript frameworks, unoptimized third-party scripts, and long-running tasks are the usual culprits. Code splitting, lazy loading non-critical scripts, and moving analytics tags to load after user interaction typically bring INP under threshold. We routinely see WordPress sites drop from 400ms to 150ms by deferring non-essential plugins. CLS tracks unexpected layout shifts caused by images without dimensions, ads that push content, or web fonts that load late. Reserve space for images and embeds with explicit width and height attributes, use font-display: swap with fallback fonts that match x-height, and avoid injecting content above existing elements. A single unoptimized ad unit can spike CLS from 0.05 to 0.3. At Ottawa SEO, we run PageSpeed Insights and Chrome's Lighthouse in field mode, prioritize fixes by impact, then validate with 28-day Field Data from Search Console. Most e-commerce and service sites need 8-20 hours of dev work to move from failing to passing all three metrics. The ranking lift is modest but measurable—usually 2-5 positions in the top 20 when competitors haven't optimized yet.