Core Web Vitals assessment is the process of measuring and analyzing three specific performance metrics Google considers critical for user experience: Largest Contentful Paint (LCP), Interaction to Next Paint (INP), and Cumulative Layout Shift (CLS). LCP tracks loading speed (target: under 2.5 seconds), INP measures interactivity responsiveness (target: under 200ms), and CLS quantifies visual stability (target: under 0.1). These became ranking signals in 2021, though they're not the heaviest factors—content relevance still dominates. You assess Core Web Vitals using four main tools. PageSpeed Insights gives you both lab data (controlled test) and field data (real user metrics from Chrome User Experience Report). Search Console shows your site-wide pass/fail rates across mobile and desktop, grouping URLs by similar templates. Chrome DevTools lets you audit individual pages in real-time and throttle connections to simulate slower networks. Finally, Lighthouse (built into DevTools or run via CI/CD) provides detailed diagnostics on what's breaking each metric. The assessment reveals specific bottlenecks: LCP failures usually trace to oversized hero images, render-blocking CSS, or slow server response times. INP issues often stem from heavy JavaScript execution, third-party scripts, or main-thread blocking. CLS problems come from images without width/height attributes, web fonts causing layout shift, or ads injecting without reserved space. At Ottawa SEO, we run assessments monthly for portfolio sites and immediately after major template changes. We focus on field data first—lab scores can be perfect while real users on 3G in rural Ontario suffer. A site might pass all three vitals but still rank poorly if content is thin, or fail all three but rank well if it uniquely answers search intent. The assessment matters most for competitive commercial queries where ten sites have comparable content. Prioritize fixes by traffic volume. Optimize your top 20 landing pages first rather than chasing a perfect score on your entire 500-page site. A homepage scoring 95 means nothing if your money pages score 40.