Browser Monitoring
Web Vitals
PerformanceObserver-backed vitals from real sessions. Charts stay empty until browsers emit vital beacons.
Metrics
Vital beacons use type: "vital" with a name and numeric value. Supported names:
LCP— Largest Contentful PaintCLS— Cumulative Layout ShiftINP— Interaction to Next PaintFCP— First Contentful PaintTTFB— Time to First ByteFID— First Input Delay (when the browser still reports it)
Optional rating (good / needs-improvement / poor) follows the metric when available.
How they arrive
installVitals runs after init. Final values flush on visibility hidden / pagehide so late LCP / CLS updates are not lost. No separate option toggles vitals — they are part of the default instrumentation set.
Dashboard
/app/browser → Performance (and Overview CWV score) aggregate observed vitals only. Tag beacons with release to compare versions — see Browser SDK.
Limitations
- Lab (Lighthouse) scores are not imported — RUM only.
- Older browsers may omit INP or still emit FID instead.
- Sampled-out sessions (
sampleRate) send no vitals.