The fastest way to check Core Web Vitals for a single page is Google PageSpeed Insights. Paste your URL, and you'll see both field data (real user measurements from Chrome UX Report over the past 28 days) and lab data (simulated test). Field data tells you what actual visitors experience; lab data helps you debug. You're looking at three metrics: LCP (Largest Contentful Paint, target under 2.5s), INP (Interaction to Next Paint, target under 200ms), and CLS (Cumulative Layout Shift, target under 0.1). For site-wide monitoring, use Google Search Console's Core Web Vitals report under Experience. It groups URLs by status (Good, Needs Improvement, Poor) and shows you which templates or page types are failing. This is the data Google actually uses for ranking, so it matters more than one-off lab tests. If you see URLs marked Poor, prioritize those. Chrome DevTools Lighthouse (right-click > Inspect > Lighthouse tab) gives you a detailed performance audit with specific recommendations. Run it in incognito mode to avoid extension interference, and test on a throttled connection (simulated Fast 3G) to see what most users experience. Lighthouse won't show field data, but it's excellent for diagnosing render-blocking resources, oversized images, or layout shifts. For ongoing monitoring, we use a combination of Search Console for trending and CrUX API or third-party tools like DebugBear or SpeedCurve for historical tracking. If you're running a 50+ page site, you need automated monitoring because Core Web Vitals can degrade after plugin updates, theme changes, or ad script bloat. One mistake: testing only your homepage. Check your highest-traffic templates (product pages, blog posts, category pages) because they often have different resource loads. A passing homepage means nothing if your moneymaker pages fail. At Ottawa SEO, we check Core Web Vitals during every technical audit and recheck monthly for portfolio sites, because Google's thresholds tightened in 2024 and will likely tighten again.