Performance monitoring and Core Web Vitals guide

Core Web Vitals are Google's page experience signals: LCP (loading), INP (interaction delay), and CLS (visual stability). When SEO consulting and technical development are planned together, these metrics are critical for both rankings and conversion.

What the metrics mean

• LCP (Largest Contentful Paint): Time until main content is visible — target ≤ 2.5s
• INP (Interaction to Next Paint): Interaction response delay — target ≤ 200ms
• CLS (Cumulative Layout Shift): Unexpected layout shift — target ≤ 0.1

Lab vs. field (RUM)

Lighthouse measures synthetically in a lab; it does not reflect real devices, networks, and geography. Search Console Core Web Vitals and RUM tools (web-vitals library, analytics integration) provide field data. Use both.

Improvement checklist

1. Images: modern format (WebP/AVIF), sizing, lazy load, priority LCP image
2. Fonts: subset, preload, font-display: swap
3. JS: code splitting, third-party script audit, defer non-critical
4. CSS: critical CSS, remove unused CSS
5. CDN and edge cache

Performance budget

Define JS bundle size and Lighthouse score thresholds in CI. Fail regressions on PR. Maintenance packages can include monthly performance reviews.

Conclusion

Performance is not a one-time optimization; it is ongoing monitoring discipline. Jettfy embeds Core Web Vitals targets in web application projects.