Landing pages
Campaign traffic is sensitive to slow first render and layout movement.
How to Monitor Core Web Vitals
Core Web Vitals help explain whether a page feels fast and stable. NorthDuty captures FCP, LCP, and CLS as part of the broader website health check.
Track the speed metrics Google cares about and catch slow deploys early.
Why Core Web Vitals need context
A slow page can be reachable and still lose visitors. Large images, blocking scripts, layout shifts, and delayed API responses can all make an otherwise online page feel broken.
Performance metrics are most useful when they sit next to the rest of the page-health picture: HTTP status, SSL, DNS, response timing, blank-page checks, failed resources, JavaScript errors, and browser-side API calls.
How NorthDuty records performance signals
NorthDuty opens each monitored page in a real Chromium browser via Playwright and records rendering metrics including FCP, LCP, and CLS. These feed directly into the health score.
Performance is 30% of the 0–100 health score, calculated as: load time × 0.6 + FCP × 0.2 + LCP × 0.2. Each metric maps to a score of 100 (good), 70 (needs improvement), or 25 (poor) using these thresholds — Full page load: good ≤1,000ms, warning ≤3,000ms; FCP: good ≤1,800ms, warning ≤3,000ms; LCP: good ≤2,500ms, warning ≤4,000ms; CLS: good ≤0.1, warning ≤0.25.
The same run also records response timing, failed resources, JavaScript errors, API calls, SSL, DNS, redirects, and blank-page status so a slow page and a broken page are visible in the same check result. Health checks run every 1, 5, or 15 minutes per project.
Where to monitor vitals first
Prioritize pages where speed and stability affect business outcomes.
Pricing and signup
Prospects may abandon when content appears late or shifts under their cursor.
Product pages
Images, recommendations, and API-driven data can slow or destabilize ecommerce pages.
App entry points
Login and dashboard shells should load quickly enough for returning users.
Best practices
Treat vitals as one signal in a wider health model.
- Watch LCP on high-traffic and conversion-critical pages
- Investigate CLS when layout shifts affect CTAs or forms
- Correlate slow runs with failed resources and API calls
- Review performance after deployments and CMS changes
- Add user journeys where slow pages affect checkout, signup, or login
- Use screenshots and visual diffs for visible layout regressions
Conclusion
Core Web Vitals are useful, but they do not explain every customer-facing failure on their own.
NorthDuty keeps vitals inside the same health record as availability, rendering, errors, API calls, UI changes, and journeys.
Related NorthDuty Pages
Keep exploring the feature pages and commercial routes connected to this topic.
Feature
Website Performance Monitoring
Monitor website performance signals, response timing, and rendering context on the pages and journeys that affect revenue, leads, and trust.
Explore Website Performance MonitoringFeature
Uptime Monitoring
Monitor uptime every 5 minutes by default with HTTP, SSL, DNS, blank-page detection, broken resources, JavaScript errors, and API call tracking.
Explore Uptime MonitoringFeature
Website Monitoring
Learn how NorthDuty combines health checks, screenshot diffs, and editable user journeys in one website monitoring project.
Explore Website MonitoringPricing
Pricing
NorthDuty pricing for website monitoring: Free, $29 Starter, $79 Pro, $199 Business, and $499 Enterprise plans.
Compare pricing plansRelated reading
More NorthDuty guides on related website monitoring topics.
Article
How to Set Up a Public Status Page
Learn how to set up a public status page for your website — what to include, how to manage incidents, and how to schedule maintenance so customers stay informed.
Read How to Set Up a Public Status PageArticle
How to Monitor Website Uptime
Learn how to monitor website uptime, choose the right checks, and catch downtime before it hurts traffic, leads, or sales.
Read How to Monitor Website UptimeArticle
Why Websites Break Without Going Offline
Learn why websites can break without going fully offline and how website health monitoring helps detect silent failures.
Read Why Websites Break Without Going OfflineFrequently Asked Questions
Short answers that summarize the practical takeaways from this guide.
Which Core Web Vitals does NorthDuty capture?
NorthDuty captures FCP (First Contentful Paint), LCP (Largest Contentful Paint), and CLS (Cumulative Layout Shift) using a real Chromium browser on every health check run.
What are the Core Web Vitals thresholds NorthDuty uses?
FCP: good ≤1,800ms, warning ≤3,000ms, poor above. LCP: good ≤2,500ms, warning ≤4,000ms, poor above. CLS: good ≤0.1, warning ≤0.25, poor above. Full page load: good ≤1,000ms, warning ≤3,000ms. Good = 100 points, warning = 70, poor = 25.
How much do performance metrics affect the health score?
Performance accounts for 30% of the total health score, using load time at 60% weight and FCP and LCP at 20% each.
How often are performance signals checked?
Website health checks run every 1, 5, or 15 minutes per project.
Call To Action
Start monitoring your website with NorthDuty today.
Use NorthDuty to monitor Core Web Vitals together with the page-health signals that explain customer impact.
Start on the free plan — add your base URL and monitoring starts in minutes.