Building blocks
Beacon
The small data packet the tracker sends to fastmon with a visit's measurements.
When a page finishes measuring, the tracker packs the metrics, timings and any errors into a compact payload and sends it, typically via the Beacon API, so delivery does not block or slow the page.
You can inspect exactly what a beacon contains with the fastmon Beacon Inspector browser extension, which is part of how fastmon keeps what it collects transparent.
Related terms
- TrackerThe lightweight script you embed once; it measures Core Web Vitals and errors directly in the browser.
- 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.
fastmon One
€99/month
1M pageviews included.
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