Building blocks
Tracker
The lightweight script you embed once; it measures Core Web Vitals and errors directly in the browser.
The tracker is the snippet that does the measuring. It hooks into standard browser APIs (the Performance API, PerformanceObserver, error events) and is aligned with the same web-vitals library Google uses, so the numbers are comparable to Chrome's.
It is small and loads without blocking rendering, so adding monitoring does not itself hurt the performance you are trying to measure.
Related terms
- BeaconThe small data packet the tracker sends to fastmon with a visit's measurements.
- Stitchfastmon's short-lived, edge-derived identifier that groups a visit without cookies or cross-site tracking.
- SessionOne continuous visit: the sequence of page views and interactions a visitor makes before going idle.
- PageviewA single page load or, in a single-page app, a route change counted as its own view.
- Collection modesPresets (Light, Standard, Full) that decide how much detail the tracker collects.
- Server-TimingAn HTTP header your backend can send to break down where server time was spent, visible in RUM.
- Cache-StatusWhether a response came from a CDN edge, the origin server or the browser cache.
Monitoring that
belongs in the EU.
Read-only by default: no cookies*, no long-lived identifiers, no US provider in the data path. Live in about five minutes.
Light
€29/month
200,000 pageviews included.
Need debugging and all features? Standard from €99 for 1M pageviews. Enterprise on request. See all plans