Core Web Vitals are three specific page experience metrics Google uses for ranking: LCP (loading speed), FID or INP (interactivity), and CLS (visual stability). Fixing them means getting 75% of your page visits into the "good" thresholds for each metric. Start with LCP, which measures how fast your largest visible element loads. Compress and serve images in next-gen formats like WebP or AVIF. Use a CDN to reduce server response time below 600ms. Preload your hero image or largest text block with <link rel="preload">. Lazy-load everything below the fold. We've seen LCP drop from 4.2s to 1.8s just by switching to WebP and enabling browser caching properly. For FID (being replaced by INP in 2024), the issue is JavaScript blocking the main thread. Defer non-critical scripts, break up long tasks, and minimize third-party tags. Google Tag Manager with 15+ tags can add 300-500ms of blocking time. Remove unused JavaScript and consider moving analytics to a lighter implementation or server-side tracking. CLS happens when elements shift after the page starts rendering. Reserve explicit width and height for images, ads, and embeds in your HTML or CSS. Avoid inserting content above existing content unless it's from user interaction. Font swapping causes CLS too, so use font-display: swap carefully or preload custom fonts. One Ottawa e-commerce client had 0.42 CLS because product images didn't have dimensions set, fixing that alone brought them to 0.06. Use PageSpeed Insights and Chrome's Lighthouse to get field data from real users (CrUX) and lab diagnostics. Field data is what counts for rankings. Test on mobile with throttled connections since 70-80% of users are on phones. Core Web Vitals affect mobile rankings more than desktop. At Ottawa SEO, we prioritize the fixes that move the needle for actual user devices, not just synthetic tests, and we track improvements in Google Search Console's Core Web Vitals report over 28-day rolling windows.